Convert Imperial Gallon to Acre-Foot
Convert imperial gallons to acre-feet instantly. 1 imperial gallon = 3.685575e-6 acre-foot — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Acre-Foot to Imperial Gallon converter for the reverse conversion.
Units explained
Imperial Gallon
The imperial gallon is defined as exactly 4.54609 liters.
Set by the British Weights and Measures Act of 1824 as the volume of 10 lb of water.
Used for fuel and beverages in the UK and Commonwealth.
UK, 1824.
Acre-Foot
An acre-foot is the volume covering one acre to a depth of one foot (1,233.48 m³).
Combines the acre and the foot for large water volumes.
The standard US unit for reservoir and irrigation water.
US water management.
Imperial Gallon to Acre-Foot conversion formula
The relationship between imperial gallons and acre-feet:
To convert imperial gallons to acre-feet, multiply the value in imperial gallons by 3.685575e-6. To reverse, multiply acre-feet by 271328.0725959055.
How to use this converter
Type a value into the calculator. The result in acre-feet updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Acre-Foot to Imperial Gallon converter for the reverse direction.
Step-by-step: convert imperial gallons to acre-feet
- Write down the value in imperial gallons (gal).
- Multiply that value by the factor 3.685575e-6.
- The product is the equivalent value in acre-feet (ac·ft).
- To reverse, multiply the acre-foot value by 271328.0725959055.
Worked examples
Example 1 — Convert 1 gal to ac·ft:
1 × 3.685575e-6 = 3.685575e-6 ac·ft
Example 2 — Convert 100 gal to ac·ft:
100 × 3.685575e-6 = 0.0003685575 ac·ft
Real-world example — Architectural to geographic scale
A 100,000-imperial gallon measurement equals one acre-foot. The five-order-of-magnitude scale change comes up in mapping work where architectural site plans must be related to road-network maps.
100000 gal × 3.685575e-6 = 0.3685575143 ac·ft
Real-world example — Small to geographic-scale
100,000 imperial gallons equals one acre-foot — a useful conversion when small-scale survey diagrams must be related to road-network distances on a different map.
100000 gal × 3.685575e-6 = 0.3685575143 ac·ft
Imperial Gallon to Acre-Foot conversion table
Standard reference values for converting imperial gallons to acre-feet:
| Imperial Gallon [gal] | Acre-Foot [ac·ft] |
|---|---|
| 0.01 | 3.685575e-8 |
| 0.1 | 3.685575e-7 |
| 1 | 3.685575e-6 |
| 2 | 7.37115e-6 |
| 3 | 1.105673e-5 |
| 4 | 1.47423e-5 |
| 5 | 1.842788e-5 |
| 10 | 3.685575e-5 |
| 20 | 7.37115e-5 |
| 30 | 0.0001105673 |
| 40 | 0.000147423 |
| 50 | 0.0001842788 |
| 100 | 0.0003685575 |
| 500 | 0.0018427876 |
| 1000 | 0.0036855751 |
Frequently asked questions
How many acre-feet is 1 imperial gallon?
How do I convert imperial gallons to acre-feet?
How do I convert acre-feet back to imperial gallons?
How many acre-feet is 100 imperial gallons?
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Metric / SI (15 units)
US Customary (Liquid) (15 units)
US Customary (Dry) (5 units)
Imperial (UK) (13 units)
Cubic (length-derived) (4 units)
Cooking / Culinary (5 units)
Sources & references
Conversion factor (1 gal = 3.685575e-6 ac·ft) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.