Alcohol Proof Converter
US proof, UK proof, and ABV both ways.
What it does
Proof doubles alcohol two different ways: America multiplies ABV by 2 while Britain multiplies by 1.75 from its gunpowder past. A 40% bourbon pours 80 at home and 70 abroad.
The tool above converts either direction between ABV, US proof, and UK proof. It returns all three numbers together.
The default 40% gives 80 US with 70 UK. The 5% beer gives 10 with 8.8, and 100 US proof reverses to 50% with 87.5 UK.
Federal gauging rules fix US proof at twice ABV with measurement tables behind every label. British proof anchors 100 at 57.15%, producing the 1.75 multiplier.
Proof sells and taxes while ABV chemistry stands still: the same bottle wears different numbers per market. Convert for the shelf you stock, then drink by ABV either way.
How to use
- Pick ABV or proof direction.
- Type the percent or proof.
- Read US proof first.
- Read UK proof beside it.
- Read ABV last.
- Label by the market.
Formula
- ABV
- Alcohol by volume percent.
- US
- US proof, twice ABV.
- UK
- UK proof, 1.75 times ABV.
TTB alcohol labeling and gauging rules define US proof at twice ABV with federal measurement standards behind it. Federal gauging manual tables in 27 CFR Part 30 carry the same proof determination. British proof traces 100 to 57.15% ABV, hence the 1.75 factor.
Worked example
Example: 40% bourbon
Default: ABV to proof, 40%.
- Bottle: 40% ABV bourbon.
- US: 40 x 2 = 80 proof.
- UK: 40 x 1.75 = 70 proof.
- Check: 100 UK proof equals 57.15% ABV.
- Reverse: 100 US proof pours 50%.
- Tool shows 80 US proof, 70 UK proof, 40% ABV.
Reference table
| ABV | US proof | UK proof |
|---|---|---|
| 5% | 10 | 8.8 |
| 40% | 80 | 70 |
| 57.15% | 114.3 | 100 |
| 75.5% | 151 | 132.1 |
Limits
- Label math, not lab assay.
- Tolerance and temp unread.
- Liqueur sugars complicate.
- Laws define markets.
Common mistakes
- Doubling for UK shelves.
- Reading proof as percent.
- Ignoring label tolerance.
- Mixing gunpowder history.
- Assuming stronger converts.
Try it yourself
Quick checks. Answers sit tucked under each question.
5% beer?
10 US proof with 8.8 UK proof.
100 US proof?
50% ABV with 87.5 UK proof.
0% ABV?
Zero proof pours water: enter ABV above 0.
Questions
US proof?
Double ABV: 40% pours 80 proof. TTB gauging rules define it.
UK proof?
1.75 times ABV: 40% pours 70 proof. 100 proof means 57.15%.
Why two proofs?
Gunpowder tests and hydrometers diverged centuries back; laws froze both.
Stronger either way?
No, proof taxes and labels while ABV chemistry stays put. Same bottle, two rulers.
Proof to ABV?
Yes, divide US proof by 2. 100 proof pours 50%.
Label exact?
No, liqueurs, labeling tolerance, and temperature corrections complicate shelf math.