125 Gallon Aquarium chart
Geometric capacity 117.8 gallons. Rated sizes are brim-full nominal; real water volume is lower after substrate and the air gap — read the chart at your actual water line.
| Depth | Gallons | Liters | % Full |
|---|---|---|---|
| 1″ | 6 | 21 | 5% |
| 2″ | 11 | 42 | 10% |
| 3″ | 17 | 64 | 14% |
| 4″ | 22 | 85 | 19% |
| 5″ | 28 | 106 | 24% |
| 6″ | 34 | 127 | 29% |
| 7″ | 39 | 149 | 33% |
| 8″ | 45 | 170 | 38% |
| 9″ | 50 | 191 | 43% |
| 10″ | 56 | 212 | 48% |
| 11″ | 62 | 234 | 52% |
| 12″ | 67 | 255 | 57% |
| 13″ | 73 | 276 | 62% |
| 14″ | 78 | 297 | 67% |
| 15″ | 84 | 319 | 71% |
| 16″ | 90 | 340 | 76% |
| 17″ | 95 | 361 | 81% |
| 18″ | 101 | 382 | 86% |
| 19″ | 107 | 404 | 90% |
| 20″ | 112 | 425 | 95% |
| 21″ | 118 | 446 | 100% |
How to measure your water volume
Measure from the inside glass bottom up to the water line — not the trim, and not from outside (glass thickness inflates the reading on small tanks). If you have substrate, measure from the top of the substrate instead and you'll get the actual water volume above it, which is the number that matters for dosing and stocking. Rated tank sizes are brim-full nominal; a typical running setup holds 10–15% less.
About this chart
Source geometry: Standard North American aquarium trade dimensions (72 x 18 x 21 in exterior-nominal).. Values are computed with exact partial-fill formulas (see methodology) — a circular/obround segment for the shell.
FAQ
How many gallons are in my 125 gallon aquarium at half depth?
About 62 gallons. Use the stick reader above for any depth.
Where do I measure from?
From the inside bottom of the tank, straight up to the wet line on your stick. Keep the stick vertical.
Why does my manufacturer chart differ by a gallon or two?
Manufacturer charts account for that tank's exact head shape and fittings; this chart is exact for the stated geometry. Differences are typically 1–3%. Rated sizes are brim-full nominal; real water volume is lower after substrate and the air gap — read the chart at your actual water line.