Proof to ABV Converter

Convert between alcohol proof and ABV instantly. Supports US Proof, UK Proof (Sikes), and Gay-Lussac (ABV) systems with bidirectional conversion, formula display, and a visual strength meter. Includes presets for bourbon, cask strength, navy strength, and Everclear.

Converter
{# ══════════════════════════════════════════════════════════ Proof / ABV Converter — Alpine.js widget ══════════════════════════════════════════════════════════ #}

Converter

ABV × 2

ABV × 1.75

% alcohol by volume

Strength

Formulas

US Proof = × 2 =

UK Proof = × 1.75 =

알코올 도수 = ÷ 2 = %

Quick Presets

{# ══════════════════════════════════════════════════════════ How-To Steps ══════════════════════════════════════════════════════════ #}

How to Use

  1. 1
    Input your proof or ABV value

    Enter the proof number or ABV percentage from your bottle label. The converter accepts both whole numbers and decimals for precision when working with cask strength or non-standard bottling strengths.

  2. 2
    Choose the conversion direction

    Specify whether you are converting from proof to ABV, ABV to proof, or between US and UK proof systems. Each direction applies the appropriate mathematical relationship or historical calibration factor.

  3. 3
    Apply the result

    Use the converted value for cocktail recipe scaling, regulatory compliance checking, or tax calculation. Distillers and importers frequently need proof conversions when preparing documentation for multiple markets simultaneously.

About

Proof is one of the most persistent historical units in the spirits world, surviving long after metric and percentage systems became dominant in most scientific and commercial contexts. The Proof to ABV Converter handles the three systems you will encounter most frequently: US Proof (twice the ABV), UK Proof (with the 57.15% reference point), and percentage ABV as used across most of Europe, Asia, and international trade.

Understanding proof is particularly important for whiskey enthusiasts navigating vintage bottles, import documentation, and cocktail recipes from different eras. An American bartender recipe from the 1930s might specify "100 proof rye," meaning 50% ABV by today's US standard. A British whisky guide from the 1970s describing a spirit as "5 degrees over proof" means 5 percentage points above 57.15% ABV, or approximately 62% ABV — a figure that maps to 124 US proof.

For home bartenders and collectors, the practical applications are equally important: scaling a cocktail recipe to account for a different proof spirit, calculating dilution needed to match a recipe's assumed ABV, or understanding how proof affects the perceived heat and body of a whiskey. The converter makes these calculations immediate and eliminates the arithmetic errors that arise when working across incompatible systems.

FAQ

How do you convert proof to ABV?
For US Proof, divide by two: 90 proof equals 45% ABV. For UK Proof (Sikes), multiply by 0.5715: 100 UK proof equals 57.15% ABV. These two formulas cover the vast majority of proof references encountered on spirit labels and in whisky literature. The converter handles both automatically, and also accounts for edge cases such as "overproof" spirits labeled at more than 100 UK proof or "underproof" at less than 40% ABV.
What is "overproof" rum, and how is it measured?
Overproof is a term originating in the UK Sikes system, where any spirit exceeding 57.15% ABV was said to be "over proof." In modern usage, overproof rum typically refers to products above 57% ABV, with some Caribbean expressions reaching 75% ABV (150 US proof). Brands such as Wray and Nephew Overproof (63% ABV, 126 US proof) and Bacardi 151 (discontinued) exemplify the category. These spirits are used in tiki cocktails to add punch without excessive dilution and are sometimes ignited for flaming presentations.
Why does the UK Sikes system use 57.15% as its reference point?
The 57.15% ABV reference originates from early 18th-century British excise practice. Revenue officers found that gunpowder moistened with spirit at exactly this concentration would still ignite reliably — a practical field test before hydrometers were widely available. Bartholomew Sikes formalized this into a legal instrument (the Sikes hydrometer) around 1816, and the 57.15% "100 proof" point became the legal standard for spirit taxation in Britain until metric adoption in 1980.
How does proof affect spirit taxation?
Excise tax on spirits is typically calculated per unit of pure alcohol rather than per volume of liquid. In the United States, the federal excise tax on distilled spirits is assessed on proof gallons (a proof gallon being one liquid gallon at 100 US proof, or 50% ABV). A 750 mL bottle of 80-proof bourbon contains 0.375 proof gallons of alcohol for tax purposes. Importers and distillers must report accurate proof figures to the TTB, making precise conversion between ABV and proof a legally significant operation.
Are there spirits above 100% ABV?
Pure ethanol is 100% ABV, and commercial spirits cannot exceed this. However, certain laboratory-grade or industrial alcohols approach absolute ethanol (99.9%+ ABV) through repeated distillation and desiccant drying. For beverage spirits, the practical ceiling is around 95% ABV due to the water-ethanol azeotrope that forms during distillation, which prevents further separation by standard atmospheric distillation. Polish Spirytus Rektyfikowany at 95% ABV (190 US proof) is among the strongest commercially available spirits.