Coralkinhonest saltwater & reef care

Free tool

Aquarium volume & displacement calculator

Your tank's rated size is not the amount of water in it. Rock and sand displace water — and every dose, salt mix and cleanup crew should be figured on your real water volume. Enter your dimensions and aquascape and we'll work out the gross, net and total-system volume.

1 · Tank dimensions

Measure the inside if you can; outside dimensions slightly overstate the volume (the glass has thickness, and you fill below the rim).

2 · Rock & sand (displacement)
3 · Sump (optional)

Only the actual water in the sump — not its empty size. Leave blank if you don't run one.

An honest tool, not a promise. The volume maths is exact geometry, but displacement is an estimate — the only exact way is to measure as you fill (count buckets or your top-off container). Use thetotal-system water figure when youdose, mix salt,size a cleanup crew orplan stock — dosing to the box's rated size is a classic way to overdose.

Displacement figures are reef-community standard estimates (rock/decor ~5–15% of volume; ~18.7 lb of dense rock ≈ 1 gal; fine sand ~60% of its bed): reef2reef & Ultimate Reef volume calculators; Reef Central / SaltwaterAquarium live-rock displacement discussions. A US gallon is exactly 231 in³; a litre is exactly 1000 cm³.