Use these reef calculators to estimate tank volume, sand, salt mix, alkalinity, calcium, magnesium, GFO, carbon, and electricity cost. Tap an icon to open a calculator. Figures are estimates — confirm with your test kits and product labels.
Handy reef math for tank volume, sand, salt mix, alk/cal/mag dosing, media, and power cost. Enter your numbers and get a clear estimate — always verify with a test kit and follow product labels.
Water Volume
Choose your tank shape and enter the measurements shown. Fill depth is how high the water is filled.
US gallons = cubic inches ÷ 231. Fill depth cannot exceed height.
Sand Bed
Pick your tank footprint shape, sand depth, and sand type to estimate how much dry sand to buy.
Weight ≈ (base area × sand depth) ÷ 1728 × density (lb/ft³). Round up to the next bag size.
Salt Mix
Estimate how much salt mix to add for a new batch or to raise salinity on existing water.
New batches usually start at 0 ppt. Mix in RO/DI and confirm with a calibrated refractometer. Approx. SG ≈ 1 + ppt/1315 at 77°F.
Alkalinity Supplement
Enter volume, current and target alkalinity, and your additive.
1 dKH ≈ 17.86 ppm CaCO₃ ≈ 0.357 meq/L. Dose slowly and retest.
Calcium Supplement
Enter volume, current and target calcium, and your additive.
Magnesium Supplement
Enter volume, current and target magnesium, and your additive.
GFO Media
Enter system volume and GFO type for a starting media amount.
Carbon Media
Enter system volume and carbon type for a starting dose.
Electric Bill
Enter your cost per kWh, then wattage, hours per day, and months per year for each device. Totals update as you type.
| Device | Wattage | Hours Used Day | Months Used Year | $ Cost Year | $ Cost Month | kWh Day | kWh Month | kWh Year | Remove |
|---|---|---|---|---|---|---|---|---|---|
| Totals | $0.00 | $0.00 | 0.00 | 0.00 | 0.00 | ||||