gallons to liters calculator
A gallons to liters calculator multiplies US gallons by 3.78541. A 50-gallon tank holds 189.27 liters (6.684 ft³); a 15,000-gallon pool holds 56,781 L.
Converting gallons to liters
A gallons to liters calculator turns a US gallon figure into its metric equivalent. Multiply the gallons by 3.78541. Liters = US gallons × 3.78541. A 50-gallon water heater holds 189.27 liters. The calculator also returns cubic feet, using ft³ = gallons × 0.133681, so the same 50 gallons is 6.684 ft³.
US containers, pools, and tanks are labeled in gallons. Chemical dosing, paint additives, and imported product sheets are often written per liter. This tool bridges the two.
Where the 3.78541 comes from
The US gallon is legally defined as exactly 231 cubic inches. A liter is exactly 1,000 cubic centimeters, and an inch is exactly 2.54 cm. Working through those definitions gives 3.785411784 liters per gallon. The calculator rounds that to 3.78541, which is accurate to well under a teaspoon even on a 1,000-gallon tank.
The cubic-foot factor comes from 231 ÷ 1,728 cubic inches per cubic foot, which is 0.133681.
Worked examples
Example 1: Water heater, 50 gallons
- Liters: 50 × 3.78541 = 189.27 L
- Cubic feet: 50 × 0.133681 = 6.684 ft³
Example 2: Backyard pool, 15,000 gallons, chemical dosed per liter
- Liters: 15,000 × 3.78541 = 56,781.15 L
- Cubic feet: 15,000 × 0.133681 = 2,005.215 ft³
- A dose of 10 mL per 100 L: 56,781 ÷ 100 × 10 = 5,678 mL, about 5.7 L
Example 3: Five-gallon bucket of sealer
- Liters: 5 × 3.78541 = 18.93 L
- If the sheet says 1 liter covers 8 m², the bucket covers about 18.93 × 8 ≈ 151 m²
Gallons to liters table
| US gallons | Liters | Cubic feet | Common container |
|---|---|---|---|
| 1 | 3.79 | 0.134 | Paint can, milk jug |
| 2 | 7.57 | 0.267 | Garden sprayer |
| 5 | 18.93 | 0.668 | Bucket |
| 10 | 37.85 | 1.337 | Small aquarium |
| 50 | 189.27 | 6.684 | Water heater |
| 55 | 208.20 | 7.352 | Steel drum |
| 100 | 378.54 | 13.368 | Small stock tank |
| 275 | 1,040.99 | 36.762 | IBC tote |
| 1,000 | 3,785.41 | 133.681 | Septic or cistern tank |
Quick mental check
To sanity-check a result without a calculator, multiply the gallons by 4, then take off 5%. For 50 gallons, 50 × 4 = 200, and 200 minus 10 is 190 liters. The exact answer is 189.27, so the shortcut lands within half a percent. If your calculated answer is nowhere near that, a unit has slipped somewhere.
US, imperial, and dry gallons
| Gallon type | Liters | Used for |
|---|---|---|
| US liquid gallon | 3.78541 | US fuel, water, paint, chemicals |
| Imperial (UK) gallon | 4.54609 | Older UK and Commonwealth labels |
| US dry gallon | 4.40488 | Rarely used, some produce measures |
Unless a label says otherwise, US products use the liquid gallon.
How to get an accurate gallon figure first
- Tanks: read the capacity plate, or measure and use the tank volume calculator.
- Pools: work out the volume from length, width, and average depth with the pool gallons calculator.
- Partial fills: a tank at 70% holds 0.7 × its rated gallons. Convert that number, not the full capacity.
Common mistakes
- Using the imperial factor on US gallons. That overstates liters by about 20%.
- Dividing instead of multiplying. Gallons to liters always makes the number bigger.
- Rounding too early. On large pools, rounding 3.785 to 3.8 adds about 220 liters per 15,000 gallons.
- Mixing mL and L in dosing. 1 liter is 1,000 mL.
- Converting the label instead of the tank. If a label gives a dose per gallon, you do not need this conversion at all; apply it to your gallon figure directly.
Related calculators
Going the other way? Use the liters to gallons calculator. For pool chemistry in gallons, try the pool chlorine calculator.
Frequently asked questions
How many liters are in a gallon?
One US gallon is 3.78541 liters. So 5 gallons is 18.93 L, 50 gallons is 189.27 L, and 100 gallons is 378.54 L.
Is a US gallon the same as an imperial gallon in liters?
No. A US gallon is 3.78541 liters and a UK imperial gallon is 4.54609 liters, about 20% more. This calculator uses the US gallon. For imperial gallons, multiply by 4.54609 instead.
How do I convert a pool's gallons to liters for chemical dosing?
Multiply the pool's gallons by 3.78541, then apply the label's per-liter rate. A 15,000-gallon pool is 56,781 liters. A product dosed at 10 mL per 100 liters would need 56,781 ÷ 100 × 10 = 5,678 mL, or about 5.7 liters.
Why does the calculator also show cubic feet?
Because tank, trench, and excavation volumes are often worked out in cubic feet. One US gallon is 0.133681 cubic feet, so 50 gallons is 6.684 ft³. That is also handy for estimating how much space a volume of water or liquid will take up.
How do I convert liters back to gallons?
Divide liters by 3.78541, or multiply by 0.264172. 100 liters is 26.417 US gallons. The liters to gallons calculator does this directly.
Estimates only. Verify quantities with your supplier before purchasing.