Tank planning
Aquarium volume calculator
Calculate aquarium capacity from external tank dimensions in centimeters, inches, liters, or gallons.
- Metric or imperial
- Tank capacity
- Water change planning
Free aquarium tools - 4 calculators
Aquarium calculators for planning and water checks.
Practical aquarium tools for estimating tank volume, planning substrate, checking NO3 and PO4 balance, and reviewing CO2 from KH and pH readings.
Which aquarium calculator is right for you?
Aquarium planning usually starts with a measurement, a substrate layout, or a water reading. Use the calculators below before changing stocking plans, buying supplies, or adjusting nutrients and CO2.
For choosing or comparing a tank
Use the Aquarium Volume Calculator when you are checking a new aquarium, comparing listed sizes, planning stocking, or estimating water change volume.
Available tool: Aquarium Volume Calculator.
For substrate and aquascape planning
Use the Aquarium Substrate Calculator before ordering aquasoil, sand, gravel, or planted tank substrate. It helps account for front-to-back slopes instead of assuming a flat bed.
Available tool: Aquarium Substrate Calculator.
For nutrient balance
Use the Nitrate & Phosphate Ratio Calculator when plants slow down, algae appears, or you want a quick sense of whether NO3 and PO4 are far from your target range.
Available tool: Nitrate & Phosphate Ratio Calculator.
For CO2 troubleshooting
Use the CO2 Calculator when KH and pH readings suggest you may be under-dosing, over-dosing, or changing CO2 too quickly for livestock comfort.
Available tool: CO2 Calculator.
When readings do not match the tank
Calculator results are planning guidance. Re-test important water values, watch livestock behavior, and make major chemistry changes gradually.
Available resources: Aquarium Tracker app, Guides, and feature pages.
How accurate are the tools?
Every result should be treated as planning guidance, not a guarantee. Tanks vary by hardscape, substrate compaction, livestock, plant mass, lighting, filtration, and test kit accuracy.
Aquascaping
Aquarium substrate calculator
Calculate substrate volume from tank footprint, front depth, rear depth, and bag size for gravel, sand, or aquasoil.
- Gravel and sand
- Aquasoil bags
- Sloped layouts
Water chemistry
Nitrate & phosphate ratio calculator
Check NO3 and PO4 balance against preset ratio targets for planted aquarium fertilizing.
- NO3:PO4 ratio
- Preset targets
- Dosing context
Plant growth
CO2 calculator
Estimate CO2 concentration from KH and pH readings for planted tank troubleshooting.
- KH and pH
- CO2 ppm
- Plant health checks
Why use these aquarium calculators?
1
Practical inputs
The calculators start with measurements and readings aquarium keepers already use.
2
Planning context
Results are paired with next-step context instead of a bare number.
3
App-ready
Use the result on the web, then track parameters, tasks, and logs in the app.
More aquarium topics
Aquarium Tracker
Track calculator results in the app.
Use a calculator on the web, then log parameters, schedule tasks, and keep tank history in Aquarium Tracker.
Get the app
Take Aquarium Tracker with you.
Download on iOS or Android to log water tests, plan maintenance, and keep calculator results close to your tanks.
Free to useBuilt for aquarium keepersSync across devices