Calculate the exact water volume of your fish tank in US gallons, Imperial gallons, and liters. Perfect for aquarium setup, fish stocking decisions, water treatments, and filter sizing. Supports rectangular, cylindrical, hexagonal, bow front, and spherical tanks.
Knowing your aquarium's exact water volume is essential for proper fish stocking, dosing medications, adding water conditioners, and selecting the right filter and heater. Our calculator converts cubic inches to gallons and liters using standard conversion factors.
Freshwater Tropical: 1 inch of adult fish per gallon
Goldfish: 1 inch per 3 gallons (they produce more waste)
Saltwater: 1 inch per 4-5 gallons (more sensitive ecosystem)
Shrimp/Snail Tanks: 10-20 small shrimp per gallon
| Tank Size | Dimensions (L×W×H) | US Gallons | Liters |
|---|---|---|---|
| Nano Cube | 10" × 10" × 12" | 5.2 gal | 19.7 L |
| 10 Gallon Standard | 20" × 10" × 12" | 10.4 gal | 39.4 L |
| 20 Gallon Long | 30" × 12" × 12" | 18.7 gal | 70.8 L |
| 29 Gallon Standard | 30" × 12" × 18" | 28.1 gal | 106 L |
| 40 Gallon Breeder | 36" × 18" × 16" | 44.9 gal | 170 L |
| 55 Gallon Standard | 48" × 13" × 21" | 56.8 gal | 215 L |
| 75 Gallon Standard | 48" × 18" × 21" | 78.5 gal | 297 L |
| 90 Gallon Standard | 48" × 18" × 24" | 89.8 gal | 340 L |
| 125 Gallon Standard | 72" × 18" × 21" | 117.8 gal | 446 L |
| 150 Gallon Standard | 72" × 18" × 28" | 157.1 gal | 595 L |
💡 Pro Tip: When calculating actual water volume, subtract displacement from substrate (gravel/sand), decorations, rocks, and driftwood. A heavily decorated 55-gallon tank may only hold 45-50 gallons of actual water. Always measure medications and conditioners based on your calculated water volume, not the tank's maximum capacity.
⚙️ Equipment Sizing Quick Guide: Heater: 2.5-5 watts per gallon. Filter: 4-6 times tank volume per hour (GPH). Lighting (planted): 2-5 watts per gallon.