Enter your tank's length, breadth, and height in any unit — get the volume instantly in litres and gallons. Useful for stocking, dosing, water changes, and choosing a filter.
Volume = L × B × H. We convert each side to metres, multiply for the volume in cubic metres, then convert: 1 m³ = 1000 L, 1 L = 0.264172 US gal, 1 L = 0.219969 UK (Imperial) gal.
Realistic volume subtracts ~15% to account for substrate, hardscape, equipment, and the water level always sitting below the rim. It's a rule of thumb, not a measurement — heavily planted or decorated tanks may lose more.
Standard footprints sold in India and abroad, with theoretical and realistic volumes.
| Footprint (L × B × H) | Often called | Capacity (L) | US gal | Realistic (L) |
|---|---|---|---|---|
| 30 × 20 × 25 cm | Nano · 1 ft | 15 | 4 | ~13 |
| 45 × 25 × 30 cm | Small · 1.5 ft | 34 | 9 | ~29 |
| 60 × 30 × 36 cm | Standard · 2 ft | 65 | 17 | ~55 |
| 75 × 30 × 36 cm | Long · 2.5 ft | 81 | 21 | ~69 |
| 90 × 38 × 45 cm | Mid · 3 ft | 154 | 41 | ~131 |
| 120 × 45 × 50 cm | Large · 4 ft | 270 | 71 | ~230 |
| 150 × 50 × 60 cm | Show · 5 ft | 450 | 119 | ~383 |
| 180 × 60 × 60 cm | XL show · 6 ft | 648 | 171 | ~551 |
| 240 × 75 × 75 cm | Statement · 8 ft | 1350 | 357 | ~1148 |
For a rectangular tank, multiply the inside length by the inside breadth and inside height (all in the same unit), then convert to litres or gallons. The calculator above does this in any unit you enter — millimetres, centimetres, metres, inches, or feet. The formula is Volume (m³) = L × B × H (in metres); multiply by 1000 to get litres.
Three things eat into the theoretical max: (1) the water never reaches the very top of the tank — most tanks are filled to ~1–2 cm below the rim, (2) substrate (sand, gravel, soil) takes up space at the bottom, typically 5–8 cm, and (3) hardscape, plants, and equipment displace more water. As a rule of thumb, plan for around 85% of theoretical capacity as the actual swimming volume for fish.
Most aquarium product labels in India use litres. If a US-made product (e.g. American filter brands) lists gallons, it's almost always US gallons. UK gallons are rare on aquarium gear today — they're listed here for completeness. 1 US gal = 3.785 L, 1 UK gal = 4.546 L.
Use inside dimensions for the most accurate volume — measure the actual water-holding cavity, ignoring glass thickness. For most home aquariums the glass is 5–12 mm, so an outside-measured tank will overestimate volume by 1–4%. Not a huge difference for stocking, but matters for precise dosing or temperature math.
The old "1 inch of fish per gallon" rule is a rough guide for community freshwater fish — but stocking depends heavily on filtration, plants, fish behaviour, and adult size, not tank volume alone. A planted 60 L tank can comfortably hold 10–15 small tetras; an aggressive cichlid might need 200 L on its own. Talk to us if you'd like advice for your specific stocking plan.
This calculator handles standard rectangular tanks, which cover ~95% of home aquariums. For a cylindrical tank, the formula is π × radius² × height. For bow-fronts, the front curve adds 5–10% over the rectangular L × B × H estimate — measure the maximum depth at the bow's center for a rough approximation. We may add shape options to this calculator later.
Need help with a tank this size? We design, install and maintain aquariums across Mumbai, Thane and Navi Mumbai.
