Free Aquarium Calculators & Tools
Quick, free tools for everyday aquarium math — no sign-up needed. Sign in with your AquaLens account to run these against your real tanks.
Most used
General
Tank Volume Calculator
Get your aquarium's volume in gallons and liters from its length, width, and height — rectangular and cylindrical tanks.
Open calculatorAquarium Unit Converter
Convert gallons ↔ liters, °F ↔ °C, dGH ↔ ppm, and dKH ↔ meq/L — the everyday conversions every aquarist needs.
Open calculatorWater Science
Water Change Calculator
Work out what percentage water change brings nitrate, ammonia, or any parameter down to your target — accounting for your source water.
Open calculatorNitrogen Cycle Helper
Enter your ammonia, nitrite, and nitrate readings to see where your cycle stands and what happens next.
Open calculatorCO₂ Level Estimator
Estimate dissolved CO₂ in a planted tank from pH and carbonate hardness, with safe target ranges.
Open calculatorHardscape Chemistry Guide
Will that rock raise your pH? How common aquarium rocks and woods affect pH, KH, and GH.
Open calculatorAquarium Dosing Calculator
Convert doses between mL, pumps, teaspoons, and grams, and scale any product label's “X mL per Y gallons” to your exact tank volume.
Open calculatorHardware & Cost
Filter Flow & Turnover Calculator
Check whether your filter's real-world flow gives your tank the turnover it needs — freshwater, planted, or reef.
Open calculatorHeater Size Calculator
Find the right heater wattage for your tank volume and the temperature rise you need above room temperature.
Open calculatorAquarium Running Cost Calculator
Estimate your tank's monthly electricity and water bill from your equipment wattage and water change routine.
Open calculatorSaltwater & Reef
Reef guides, coral and fish species, and the full saltwater toolkit live in the Saltwater & Reef hub.
Salinity Converter
Convert between specific gravity and ppt for saltwater and reef tanks, with the standard reef target range for reference.
Open calculatorSalt Mix Calculator
How much salt mix to add to reach your target salinity — for new saltwater batches and top-ups.
Open calculatorReef Dosing Calculator
See how far your alkalinity, calcium, or magnesium is from the reef range and how many days a correction takes to make safely — then scale the dose from your own supplement.
Open calculatorStocking
Aquarium Stocking Calculator
Plan a stable community around adult size, social needs, swimming room, filtration, and maintenance—not an arbitrary fish count.
Build a planSchooling Group Size Checker
Look up the minimum group size for any schooling or shoaling fish, and see why that number is a floor rather than a target.
Open calculator