Free calculators for reef tank math. No sign-up, nothing to install, and every result explains the formula behind it.
Dosing calculator
How much 2-part, soda ash, baking soda, calcium, or magnesium product to dose to reach your target.
Tank volume calculator
Gallons and liters from your dimensions, minus rock and sand, plus sump and water weight.
Salinity converter
Parts per thousand to specific gravity and back, at 77 掳F or 60 掳F.
Water change calculator
What a water change does to nitrate, phosphate, and alk, and what size hits your target.
Start with the volume calculator if you're not sure how much water your system really holds. Every dose depends on it.