AQUARIUM CALCULATOR PRO
Stunning planted aquarium aquascape

Plan your perfect aquarium.

The free aquarium calculator and fish tank planner trusted by hobbyists worldwide. Calculate volume in gallons or litres, check glass thickness, stock fish safely with a 125+ species bioload checker, plan plants & CO2, size your heater, and export printable blueprints — all in one place, no download needed.

Dimensions & Volume

Substrate Volume Displacement ⓘ

Gross Volume
-- L -- gal
Substrate Displaced
-- L -- gal
Net Water Volume
-- L -- gal

Real-time Tank Dimensions

Drag to rotate · Scroll to zoom

Structural Thickness

ⓘ
Recommended Glass
-- mm -- in
Bowing: -- mm -- in
Recommended Acrylic
-- mm -- in
Bowing: -- mm -- in

Fish Stocking & Bioload Calculator

Stocking List
Species Qty Bioload Temp (°C)Temp (°F) pH Action
No fish added yet. Search and select species to design your bioload.
Bioload Stocking Density Capacity 0% (Empty)
0% Empty 80% Warning Threshold 100% Maximum Target Limit

Biological Parameter Check & Compatibility

✓ System Parameters Check: Temperature, pH values, bioload levels, and aggression levels are all fully balanced.

Weekly Water Change Estimator ⓘ

Recommended Weekly Water Change
0%
0 L 0 gal
Add some fish to get a custom recommendation.

Interactive Nitrate Simulator

25%
Post-Change Nitrate
-- ppm
--
Est. Nitrate Accumulation
+0 ppm/wk
Standard rate

Plant Compatibility, Light/PAR, & CO2 Planner

Easy Medium Advanced
Selected Vegetation
No plants selected. Use check-list to add aquatic vegetation.
🌿 Required PAR Target (Substrate)
15 - 30 µmol/m²/s
Low Intensity LED
🫧 Target CO2 Bubble Rate
0 Bubbles / sec
None / Low-Tech setup

pH-KH CO2 Calculator

ⓘ

Enter your measured pH and Carbonate Hardness (KH) to find the dissolved CO2 concentration in your water.

Calculated dissolved CO2
-- ppm
--

Filter Flow Rate Calculator

Turnover rate is calculated dynamically based on net water capacity, active bioload rating (highest species level), and CO2 vegetation settings.

Recommended Turnover Rate
-- L/h -- GPH
Target turnover: --x volume per hour
Ecosystem state: Standard Setup

Heater Wattage Calculator

ⓘ

Heater wattage is estimated based on the temperature difference (ΔT) between your target aquarium temperature and the ambient room temperature. The calculator uses your net water volume from Section 1 and the temperature inputs below.

70°F 21°C
77°F 77°C
Temperature difference (ΔT): --
Net Water Volume:
L
Recommended Heater Power
-- W
Rule of thumb (3-5 W/gal): -- W
Recommended Setup --

Sizing Reference Guide

Tank Volume Mild ΔT (≤5°C / 9°F) Moderate ΔT (5-10°C / 9-18°F) High ΔT (>10°C / 18°F)
Up to 40 L (10 gal) 25 W 50 W 75 W
40-80 L (10-20 gal) 50 W 75-100 W 100-150 W
80-150 L (20-40 gal) 100 W 150-200 W 200-250 W
150-250 L (40-65 gal) 150-200 W 200-300 W 300-400 W
250-400 L (65-105 gal) 200-250 W 300-400 W 2 × 300 W
400-600 L (105-160 gal) 300 W 2 × 250 W 2 × 400 W

Best Practices & Safety

  • Redundancy: For tanks requiring >200 W, use two smaller heaters instead of one large one. If one fails, the other maintains a safe temperature.
  • Placement: Place heater near water flow (filter outlet or circulation pump) for even heat distribution.
  • Submersion: Always fully submerge the heater below the minimum water line — never run a heater partially exposed.
  • Controller: Use a separate thermostat or temperature controller for critical setups — built-in thermostats can fail.
  • Cover: A glass canopy or lid reduces heat loss, especially in rooms with air conditioning or drafts.
  • Acclimation: When changing water, let the new water reach tank temperature before adding to avoid thermal shock to fish.

Temperature by Biome

Tropical Community
24-27 °C / 75-81 °F
Tetras, Rasboras, Guppies, Corydoras
Discus / Altum
28-30 °C / 82-86 °F
Discus, Cardinals, Rummy Nose
Cold Water
15-22 °C / 59-72 °F
White Clouds, Danios, Goldfish
High-Tech Planted
24-26 °C / 75-79 °F
Optimal for CO₂ injection & growth
Official Specification Sheet

Aquarium Blueprint.

1. Physical Configuration

Tank Shape: Rectangular
Dimensions: --
Gross Volume: -- L -- gal
Net Water Capacity: -- L -- gal
Substrate: -- L -- gal
Hardscape: -- L (-- kg) -- gal (-- lbs)

2. Structural Material Safety

Safety Factor Setting: --
Glass Thickness: --
Acrylic Thickness: --
Construction Bounds: Safe / Rimless
Glass Weight: --
Total Weight (filled): --
Substrate to Buy: -- L (-- kg) -- gal (-- lbs)

3. Parameter Target Ranges

Target Temperature: -- °C -- °F
Recommended Heater: --
Target pH Range: --
Bioload Capacity State: 0% Safe
Est. Weekly Water Change: --

4. Vegetation & CO2 Setup

Light Target PAR: --
CO2 Target Rate: --
Measured CO2 (pH-KH): -- ppm
Filtration Turnover: -- L/h -- GPH

Stocked Fauna Checklist

  • No species added.

Planted Flora Checklist

  • No plants selected.

Substrate Volume to Buy

Substrate Volume
-- L -- gal
liters to purchase
gallons to purchase
Substrate Weight
-- kg -- lbs
based on substrate type
Substrate density reference: Soil ≈ 0.9 kg/L · Gravel ≈ 1.6 kg/L · Sand ≈ 1.5 kg/L

Hardscape Estimator ⓘ

Select a stone type to see details.
Select a wood type to see details.
Hardscape Weight
0.0 kg 0.0 lbs
Water Displaced
0.0 L 0.0 gal

Weight Estimate (Filled Aquarium)

Total approximate weight for furniture and stand planning.

Total Filled Weight
-- kg -- lbs
Water Weight
-- kg -- lbs
1 L = 1 kg
1 gal ≈ 8.34 lbs
Glass Weight
-- kg -- lbs
density 2.5 g/cm³
Substrate Weight
-- kg -- lbs
based on type
Hardscape Weight
-- kg -- lbs
stone & wood
🪨 Stand load recommendation: Choose a stand rated for at least -- kg-- lbs to ensure a sufficient safety margin. Always verify floor load capacity for large tanks.
All-in-one aquarium planning tool

The Complete Free Aquarium Calculator Suite

Setting up a fish tank should be exciting, not stressful. Aquarium Calculator Pro is a free, browser-based aquarium planner that takes the guesswork out of every decision — from choosing the right glass thickness for a rimless build to figuring out how many cardinal tetras actually fit in a 20-gallon tank. Whether you're a first-time fishkeeper or a seasoned aquascaper, every calculation you need is right here. No app download required, no sign-up, just instant results in gallons, litres, or any unit you prefer.

Aquarium Volume Calculator — Rectangular, Bowfront, Cylinder & Hexagonal Tanks

Wondering how many gallons your fish tank holds? Our aquarium volume calculator supports rectangular, bowfront, cylinder, and hexagonal tank shapes. Enter your dimensions in centimetres, inches, or feet and instantly see the gross volume, substrate displacement, and true net water capacity. The built-in substrate calculator figures out exactly how much soil, gravel, or sand you need — including sloped beds for aquascaping — so you buy the right amount the first time. A real-time 3D aquarium visualizer lets you see your tank come to life as you adjust dimensions.

Glass Thickness & Acrylic Safety Calculator

Building a DIY aquarium or checking if your rimless tank is safe? Our glass thickness calculator uses the industry-standard plate-bending formula to recommend safe panel thickness for both glass and acrylic builds. Choose your safety factor — from standard braced setups to heavy-duty rimless designs — and see the recommended thickness in millimetres along with the expected bowing deflection. The calculator flags when euro-bracing or custom reinforcement is needed, so you can prevent structural failures before they happen. All the complex engineering math is done for you behind the scenes.

Fish Stocking Calculator & Bioload Compatibility Checker

Overstocking is the number-one mistake new fishkeepers make. Our aquarium stocking calculator features a built-in database of over 125 freshwater species — from nano fish like ember tetras and chili rasboras to larger cichlids and plecos. Add fish to your virtual tank, and the bioload calculator instantly shows your stocking density as a percentage, flags temperature and pH conflicts between species, and checks aggression compatibility. A weekly water change estimator and interactive nitrate simulator help you keep water chemistry healthy week after week.

Planted Tank Planner — CO2, PAR Lighting & Filter Flow Rate

Growing a lush planted aquarium is easier when you know your numbers. Browse our aquatic plant database covering easy, medium, and advanced species, and the planner automatically calculates the PAR lighting target your plants need at substrate level. Growing high-tech? The CO2 calculator shows you the ideal bubble rate, while the pH-KH dissolved CO2 chart tells you exactly where your concentration sits. The filter flow rate calculator recommends the right turnover speed based on your tank volume, bioload, and whether you're running a low-tech or CO2-injected setup.

Aquarium Heater Wattage Calculator & Weight Estimator

What size heater do you need? Our heater wattage calculator sizes your aquarium heater based on the temperature difference between your room and your target tank temperature — whether you measure in Celsius or Fahrenheit. On the weight side, the filled aquarium weight calculator totals up water, glass, substrate, and hardscape so you know exactly how heavy your tank will be. Use those numbers to verify your aquarium stand weight capacity and make sure your floor can handle the load before you fill up.

Printable Aquarium Blueprint & Specification Sheet

Once you've dialled in every setting, export a complete aquarium specification sheet as a printable blueprint. It summarises your tank dimensions, glass thickness, stocking list, target temperature and pH ranges, CO2 setup, heater wattage, filtration turnover, and weekly water change recommendation — everything you need on a single page. Use it as a shopping checklist at the fish store, a reference sheet taped to your stand, or a setup guide to share with fellow hobbyists. It's the aquarium setup checklist you didn't know you needed.

Why Hobbyists Choose Aquarium Calculator Pro

Because healthy fish start with good planning. Every calculator works together — change your tank dimensions and the stocking limits, heater wattage, and filter flow rate all update instantly. No more switching between five different websites or second-guessing forum advice. Aquarium Calculator Pro is the complete, free aquarium planning tool built for real hobbyists — from your first community tank to your dream high-tech planted aquascape.

Knowledge Base

Frequently Asked Questions

Expert answers to the most common aquarium planning questions — from calculating tank volume in gallons to sizing your heater, stocking fish safely, and choosing the right glass thickness.

Volume & Dimensions

How do I calculate the true water volume of my aquarium?

Measure the internal length, width, and height of your tank in centimetres, then use the formula: Volume (litres) = L × W × H ÷ 1000. For non-rectangular shapes such as bowfront or hexagonal tanks, our aquarium calculator adjusts the base-area formula automatically. Subtract substrate displacement (gravel or sand depth × base area) to get the net water volume available for fish and filtration.

How many gallons is my fish tank based on its dimensions?

Enter your tank's length, width, and height into the fish tank gallon calculator. The tool computes gross volume in litres first, then converts: 1 US gallon = 3.785 L. A standard 60 × 30 × 36 cm tank is approximately 65 litres or 17.2 US gallons. Remember that substrate and decorations reduce this figure by 10–20% in a planted setup.

Should I measure the inside or outside of the tank to calculate volume?

Always measure the inside (interior) dimensions. Glass panels add 6–19 mm per side depending on thickness. Measuring exterior dimensions and then subtracting twice the glass thickness for each dimension gives the true water volume. Our calculator includes a glass-offset field that performs this correction automatically.

How do I calculate the volume of a bow-front or hexagonal fish tank?

For a bow-front aquarium, the calculator uses the trapezoid approximation: base area = ((front width + back width) / 2) × depth. For a hexagonal prism tank, the formula is: base area = (3√3 / 2) × s², where s is the flat-to-flat width divided by √3. Select the matching shape in our aquarium size chart calculator and enter the requested dimensions — the correct formula is applied automatically.

Why is my actual tank water volume less than the advertised gallons?

Manufacturers state gross nominal volume measured from outside edges at full depth. In practice, glass thickness, substrate (gravel or sand), rocks, driftwood, filter equipment, and an air gap below the waterline all displace water. A well-planted 100-litre (26 gal) aquarium may hold only 70–80 litres of actual water. Use our fish tank water capacity calculator with the substrate offset to get the true net volume.

Glass Thickness & Structure

How thick should the glass be for a custom aquarium?

Glass thickness for aquariums is calculated using the plate-bending formula: t = √(SP × h² / (0.75 × E)), where SP is water pressure, h is the longest unsupported panel height, and E is the allowable bending stress for glass (~19 MPa with a safety factor of 3.8). Our aquarium glass thickness calculator outputs the minimum recommended thickness in millimetres, then rounds up to the nearest standard glass size (4, 5, 6, 8, 10, 12, 15, 19 mm).

What is the safety factor in aquarium glass thickness calculations?

The safety factor divides the allowable bending stress used in the thickness formula. A factor of 3.8 is the DIY and rimless standard (recommended default). Use 4.0 for extra conservatism on large rimless builds, 3.0 for fully braced Euro-brace tanks, and 2.5 only for smaller braced tanks where deflection is mechanically constrained. A higher safety factor results in a thicker — and safer — glass recommendation.

Is rimless aquarium glass thicker than standard braced tanks?

Yes. Without a top frame or cross-brace to distribute hydrostatic pressure, each glass panel in a rimless build bears the full bending load from water. Our how thick glass for aquarium calculator automatically applies the higher safety factor of 3.8–4.0 for rimless builds versus 2.5–3.0 for braced tanks, which typically results in 2–4 mm thicker panels for the same tank dimensions.

How do I calculate the bowing or deflection of acrylic fish tanks?

Acrylic deflection is calculated using the same plate-bending equations, but with acrylic's Young's modulus (~3 GPa vs. glass's ~70 GPa). This means acrylic flexes significantly more for the same thickness. Our calculator outputs the expected panel deflection (bow) in millimetres. For acrylic tanks, the maximum recommended deflection is L/250, where L is the panel's long edge, to avoid permanent deformation or silicone joint stress.

Substrate & Weight

How much sand or gravel do I need for my fish tank?

Use the aquarium gravel calculator formula: substrate volume (L) = base area (cm²) × depth (cm) ÷ 1000. Then multiply by bulk density: coarse gravel ≈ 1.5 kg/L; sand ≈ 1.6 kg/L; aqua soil ≈ 0.65 kg/L. A 60 × 30 cm base with 5 cm of gravel needs 9 litres or about 13.5 kg. Our how much sand for aquarium calculator handles all substrate types and slope configurations.

How do I calculate the amount of soil needed for a sloped aquascape?

For a sloped substrate bed, the calculator averages front and back depths: Volume = base area × ((front depth + back depth) / 2). For example, a 60 × 30 cm tank with a 2 cm front slope and 8 cm back yields a volume of 60 × 30 × 5 cm (average) = 9 litres of soil. Enable the slope toggle in the substrate section and enter front and back depths individually.

How much does a filled aquarium weigh?

Total weight = (tank dry weight) + (water volume × 1 kg/L) + (substrate kg) + (rock & driftwood kg) + (equipment kg). Water weighs 1 kg per litre (8.34 lb per US gallon). A 200-litre (53 gal) tank with substrate and rocks typically weighs 250–280 kg (550–620 lb) when filled. Always verify your stand and floor rating against this total loaded weight before setting up a large aquarium.

Will my floor or stand support the weight of my fish tank?

Residential floors in most modern homes are rated for 200–400 kg/m² (40–80 lb/ft²). A 200-litre filled aquarium concentrates roughly 250–280 kg over the footprint of its stand (~0.18 m²), equalling ~1,400 kg/m². Position the stand against a load-bearing wall, run it perpendicular to floor joists, or use a purpose-built aquarium stand rated for the total loaded weight. For tanks over 400 litres, consult a structural engineer.

How much water volume do rocks and driftwood displace in an aquarium?

Rock displaces approximately its own volume in water: 1 kg of average aquarium rock ≈ 380 mL. Driftwood is variable; waterlogged wood displaces very close to its own volume (~1 L per kg), while dry driftwood first floats before sinking after waterlogging. Measure rock displacement by the water-level rise method: fill a bucket to a known mark, add the rock, and measure the rise. Our substrate & weight panel lets you enter a total rock/decoration displacement offset in litres.

Fish Stocking & Bioload

How many fish can I safely put in my aquarium?

Use our how many fish in aquarium calculator, which uses a bioload scoring system rather than the simplistic inch-per-gallon rule. Each species is assigned a bioload score based on body shape, adult size, diet, and waste output. The target is ≤100% of the tank's calculated bioload capacity, with a warning threshold at 80%. A 60-litre tank can safely hold a bioload score of up to 60 points — for example, 8 ember tetras (0.5 pt each) plus 6 pygmy corydoras (1 pt each) = 10 points total, well within capacity.

Is the one inch of fish per gallon rule still accurate?

No — the 1 inch per gallon rule is a rough and often misleading heuristic developed for small community fish in the 1950s. It fails for wide-bodied fish (goldfish, cichlids), tall fish (discus, angelfish), and high-waste species. Modern fishkeeping uses bioload scoring, surface area, and filtration turnover rate as more accurate stocking metrics. Our fish tank gallon calculator uses per-species bioload coefficients for 125+ species.

How do I calculate the bioload capacity of my fish tank?

Bioload capacity is primarily determined by the nitrogen cycle efficiency of your filtration and the dissolved oxygen levels at your water's surface. As a guideline, our calculator assigns a capacity of 1 bioload point per litre of net water volume. Each species entry has a pre-set bioload coefficient (light, moderate, or heavy). Heavy bioload fish like goldfish or large cichlids rate 3–5× higher than similar-sized tetras.

Do live aquatic plants reduce the bioload in an aquarium?

Yes. Live plants consume ammonia and nitrate directly as plant fertiliser through the nitrogen cycle, reducing the biochemical oxygen demand on your filter. A heavily planted tank (>50% plant coverage) can support approximately 20–30% more bioload than an equivalent unplanted tank. Our calculator applies a plant bonus modifier to bioload capacity when you select plants in the Plant Planner tab.

How do I check if my aquarium fish are compatible with each other?

Our compatibility checker evaluates three parameters for every fish combination in your stocking list: (1) temperature overlap — all species' minimum–maximum ranges must intersect; (2) pH overlap — all pH ranges must share a common value; (3) aggression flags — species tagged as fin-nippers, territory-holders, or predators trigger warnings against vulnerable tank-mates. Conflicts are highlighted in the Biological Parameter Check panel with specific species callouts.

Heater, Filter & CO2

What size heater in watts do I need for my aquarium?

Use our aquarium heater calculator: Wattage = Net Volume (L) × ΔT (°C) × 0.25. ΔT is the difference between your target tank temperature and the minimum ambient room temperature. A 100-litre tank targeting 26°C in a room that drops to 20°C (ΔT = 6°C) needs 100 × 6 × 0.25 = 150 W. Always size up to the next standard heater wattage (e.g., 200 W) for headroom and redundancy.

How many watts per gallon should an aquarium heater be?

The watts-per-gallon guideline is 2.5–5 W/US gallon for most tropical tanks. The lower end (2.5 W/gal) applies to smaller temperature differentials (ΔT ≤ 5°C), while the upper end (5 W/gal) applies to tanks in cold rooms or species needing high temperatures (28–30°C). Our aquarium heater calculator uses the precise thermal formula rather than a flat W/gallon estimate, which is more accurate across a wider range of tank sizes and room conditions.

How do I calculate the correct filter flow rate for my tank?

The recommended filter turnover rate is: Flow Rate (L/h) = Net Volume × Turnover Multiplier. Use 4× turnover for lightly stocked community tanks, 6× for moderately stocked tanks, 8–10× for heavily stocked or high-bioload setups, and 10–15× for cichlid tanks or sumps. Our filter flow rate calculator derives the multiplier dynamically from your stocking bioload rating and plant settings, then outputs the target L/h or GPH rating to look for when purchasing a filter.

How many bubbles per second of CO2 does my planted tank need?

CO2 bubble rate depends on tank volume, plant density, and light intensity. A common starting point is 1 bubble per second per 50 litres for a medium-tech planted tank. Our CO2 calculator determines your target dissolved CO2 concentration (ideally 15–30 ppm for high-tech plants) from your pH and KH readings using the formula: CO2 (ppm) = 3 × KH (dKH) × 10^(7 − pH). The plant planner then recommends a bubble rate in bubbles-per-second based on your plant selection and tank volume.

How do I calculate the weekly water change percentage for my aquarium?

Weekly water change recommendation = bioload density × base rate. At low stocking (≤40% bioload): 10–15% weekly. At moderate stocking (40–70%): 20–25% weekly. At high stocking (>70%): 30–50% weekly. Our weekly water change estimator adjusts this using your actual stocking list bioload score, plant modifier, and pre-change nitrate level from the Interactive Nitrate Simulator, giving you a personalised volume in litres or gallons to remove and replace each week.