Exact aquarium math, no guesswork.
No more estimating. Get precise calculations for tank volume, floor load, stocking capacity, and CO₂ injection.
Aquarium Calculators.
Select a tool below to calculate exact tank capacity, stocking capacities, structural weight, or chemical dosing parameters.
Tank Volume Calculator
Calculate exact water volume in US Gallons, Liters, and UK Gallons for Rectangular, Bowfront, Cylinder, Hexagon, and Cube tanks.
Stocking Level Calculator
Estimate safe bio-load capacity based on fish length, surface area gas exchange, and filtration turnover rate.
Filled Tank Weight Calculator
Determine combined load of water, glass thickness, substrate, and equipment to ensure safe floor joist placement.
CO₂ Bubble Rate Calculator
Calculate target CO₂ bubble rates per minute targeting 30 ppm dissolved CO₂ using pH and dKH water hardness metrics.
Substrate & Soil Calculator
Determine required pounds, kilograms, or bag counts (9L soil / 5lb retail) of aqua-soil, sand, or gravel for target bed depth.
Liters ↔ Gallons Converter
Convert aquarium volumes between liters, US gallons, and UK gallons instantly with freshwater weight per conversion.
Heater Wattage Calculator
Size your aquarium heater based on tank volume, room temperature, and target water temperature with split-heater advice.
Filter Flow Calculator
Calculate required filter GPH and turnover rate for your tank volume, water type, and filtration level.
Essential aquarium constants.
How to plan an aquarium setup without guessing.
Start with real volume
Every other number — stocking, weight, heater size, filter flow — depends on how much water your tank actually holds, not the number printed on the box. Measure the interior glass, pick your shape, and use the tank volume calculator to get gross and net volume. If you're comparing tanks in litres and gallons, the liters ↔ gallons converter handles the exact conversion including UK imperial gallons.
Size the structure and equipment
Water is surprisingly heavy at 8.34 pounds per US gallon. A filled 55 gallon commonly exceeds 600 pounds once glass, substrate, and stand are included, so check your floor and stand before filling. Then size the heater and filter flow against the real volume, not the label. Substrate depth comes next — the substrate calculator converts footprint and bed depth into the bags you'll actually carry home.
Stock conservatively
The one-inch-per-gallon rule is a rough ceiling, not a target. Plan around adult sizes, group minimums, and how much maintenance you'll actually do. The stocking calculator turns your net volume and filter turnover into a safe bioload estimate, and the stocking guide gives realistic plans for 10, 20, 30, and 55 gallon community tanks. For planted tanks, read the CO₂ injection guide before you buy a regulator.
Built on verified aquatic fluid standards.
Every calculator on AquaCalc uses calibrated fluid dynamics and bio-load constants derived from standard aquatic chemistry benchmarks:
- 01/ Water Density: 8.34 lbs / US Gal (1.00 kg/L at 25°C)
- 02/ CO₂ Equilibrium: pH - log10(dKH) Henderson-Hasselbalch
- 03/ Substrate Density: ~1.4 - 1.6 kg/L for Aqua-Soil & Sand
// Recommended Planted Tank CO2 Targets (Target = 30 PPM) { "dKH_1.0": { "pH_6.0": "30 ppm (OPTIMAL)", "pH_6.4": "12 ppm (LOW)" }, "dKH_4.0": { "pH_6.6": "30 ppm (OPTIMAL)", "pH_7.0": "12 ppm (LOW)" }, "dKH_8.0": { "pH_6.9": "30 ppm (OPTIMAL)", "pH_7.3": "12 ppm (LOW)" } }
Frequently asked questions.
How AquaCalc works, what it does with your data, and how much confidence to place in each type of result.