How is UK Proof to US Proof calculated?

Both scales are normalized through ABV percent, then converted using a fixed ratio.

Is the mirror direction available?

Yes. Use the switch button or open the US Proof to UK Proof page.

Can I use decimal inputs?

Yes. Decimal strength values are supported for lab, labeling, and mixology use cases.

proof (UK) to proof (US)

1 UK Proof = 1.143 US Proof · fixed factor via canonical reference constants · no offset

Direct Answer

1 UK Proof equals 1.143 US Proof

This conversion uses a fixed factor based on canonical reference constants.

For 0.25 UK Proof, the result equals 0.28575 US Proof.

Converter Calculator

UK Proof (proof (UK))

1 UK Proof (proof (UK)) =
1.143 US Proof (proof (US))

Explanation

Multiply by 1.143 because 1 proof (UK) corresponds to 0.5715% ABV and 1 proof (US) corresponds to 0.5% ABV. 100 UK proof equals 57.15% ABV. US proof is defined as 2 times ABV.

UK Proof to US Proof follows one canonical fixed-factor definition tied to canonical reference constants, keeping calculator output and table values aligned.

Table rows are generated from the same conversion constants used by the live calculator to maintain deterministic results.

Method & Reference (Verified)

Method basis: UK Proof to US Proof uses the page-specific conversion model shown in Direct Answer.
Applied factor: 1 UK Proof = 1.143 US Proof (as defined for this route).
Consistency rule: calculator output and table values use the same constants and rounding policy.

Common Conversion Values

UK Proof (proof (UK))	US Proof (proof (US))
0.25	0.28575
0.5	0.5715
1	1.143
5	5.715
12	13.716
20	22.86
40	45.72
57.15	65.32245
80	91.44
100	114.3