Alcohol Proof Converter
Convert between alcohol by volume (ABV), US proof and UK proof instantly. Enter any strength value and see all three equivalent units plus a context for how strong that drink is.
Convert Between Proof and Alcohol by Volume
Alcohol Proof
Where:
- \(\text{ABV}\) — alcohol by volume, the percentage of the total volume that is pure ethanol
- \(\text{US proof}\) — the American proof scale, where pure (100%) alcohol equals 200 proof
- \text{UK proof} — the British proof scale, where 100 proof equals approximately 57.06% ABV
These two simple relationships let you move between the three systems in either direction. Whichever unit you start from, the calculator first converts the value to ABV and then derives the other two.
Alcohol Proof – Calculation Example
Example: a bottle of vodka is labelled 40% ABV. What is its strength in US and UK proof?
\[ \text{US proof} = 2 \times 40 = 80 \]
\[ \text{UK proof} = 40 \times \frac{7}{4} = 70 \]
Result: 40% ABV = 80 US proof = 70 UK proof. This is the standard bottling strength for most spirits sold in the US and Europe.
How to use the calculator
- In the “I have a value in” dropdown, choose the unit your number is expressed in: Alcohol by volume (%), US proof or UK proof.
- Enter your figure in the “Value to convert” field — for example 40 for a typical spirit, or 80 if you have a US proof figure.
- Read the “Equivalent alcohol strengths” table, which shows your value converted into all three units and marks the one you entered.
- Check the “Strength context” line to see what type of drink that strength corresponds to, from beer to near-pure alcohol.
What is alcohol proof?
Alcohol by volume (ABV) is the modern, international way of expressing the strength of an alcoholic drink: it is the share of the beverage's total volume that is pure ethanol. A drink at 40% ABV contains 40 ml of pure alcohol in every 100 ml of liquid. ABV is the standard on labels throughout Europe, most of Asia and Latin America, and increasingly everywhere else.
Proof is an older measure, and it means different things depending on where you are. In the United States, proof is simply double the ABV percentage — so 80 US proof is 40% ABV, and 200 US proof would be pure alcohol. This system came from a 19th-century British tradition of “proof spirit”: gunpowder wet with spirit of sufficient strength would still ignite, “proving” the alcohol content. The modern US scale formalised the ratio at 2:1.
The United Kingdom used a different, more complex scale, defined so that 100 UK proof equals exactly 57.06% ABV by volume. In round terms, UK proof is ABV multiplied by 7⁄4. So the same 40% ABV vodka that is 80 US proof is 70 UK proof — a reminder that proof numbers are meaningless without knowing which country's scale is being used. The UK switched to ABV for labelling in 1980, but old books, classic cocktail recipes and some historical or export bottles still quote UK proof.
The calculator also gives you a sense of scale: below about 5% ABV you are in beer territory, 11–14% is typical table wine, 17–22% is fortified wine, 40% is the standard strength for spirits, and anything above 60% is cask-strength or overproof territory that should be handled and sipped with care.
Typical strengths reference table
| Drink | ABV | US proof | UK proof |
|---|---|---|---|
| Light beer | 4% | 8 | 7 |
| Table wine | 12% | 24 | 21 |
| Port / sherry | 20% | 40 | 35 |
| Vodka / gin / whisky | 40% | 80 | 70 |
| Cask-strength whisky | 60% | 120 | 105 |
| Overproof rum | 75.5% | 151 | 132.1 |
Assumptions and limitations
- US proof is exact: the relation US proof = 2 × ABV is a legal definition, so those conversions carry no rounding error beyond the decimals shown.
- UK proof is approximate in practice: the historical scale was defined by density rather than volume fraction. The calculator uses the standard 7:4 ratio (100 UK proof = 57.06% ABV), which matches how the scale is almost always quoted today.
- ABV is capped at 100%: pure ethanol is 200 US proof or about 175.1 UK proof. Ordinary distillation cannot exceed roughly 95.6% ABV because ethanol and water form an azeotrope, so no real beverage reaches the top of the scale.
- Proof is not a measure of “how drunk”: it describes concentration, not the total alcohol you consume. A large glass of wine can contain more alcohol than a shot of spirits.
- Label values are nominal: legal tolerances allow a small deviation between the stated and actual ABV, and some wines change slightly after bottling.
Related calculators
If you are working with homemade drinks, our Brewing ABV calculator estimates the final alcohol content from gravity readings, and the Brix to specific gravity converter helps with the sugar measurements behind fermentation. For other everyday unit conversions, try the PPM converter.
Frequently Asked Questions
What does "80 proof" mean on a bottle label?
If the label is American, 80 proof simply means the bottle contains 40% alcohol by volume — proof is just the ABV percentage doubled. So 100 proof US is 50% ABV, and 151 proof rum is 75.5% ABV. If you see a proof figure on an old British book or historic bottle, remember it uses a different scale: 100 UK proof is only about 57% ABV, not 50%.
How do I convert proof to ABV in my head?
For US proof, halve the number: 80 proof ÷ 2 = 40% ABV. Going the other way, double the ABV. For UK proof the mental math is harder because the ratio is 7:4 — dividing UK proof by 7 and multiplying by 4 gives ABV, so 70 UK proof is (70 ÷ 7) × 4 = 40% ABV. A quick sanity check: UK proof numbers always run lower than US proof for the same drink.
Is ABV the same as alcohol by weight (ABW)?
No. ABV measures the volume share of ethanol, while ABW measures its weight share. Because ethanol is lighter than water (density about 0.789 g/ml), ABW figures come out lower: a 4% ABV beer is roughly 3.2% ABW. Some older US state beer laws and a few labels quote ABW, so check which one you are reading before comparing strengths.
What proof is considered strong for a spirit?
Standard vodka, gin, rum and whisky are 80 US proof (40% ABV). Bottles in the 100–120 proof range are already noticeably stronger than standard, and anything above 120 proof — cask-strength whiskies and overproof rums — is meant for dilution, mixing or very careful sipping. High-proof spirits also carry a bigger risk of overpouring, since a small volume contains a lot of ethanol.
Does a higher-proof drink always get you drunk faster?
Not by itself. Proof only tells you the concentration of alcohol, not how much you actually drink. A 5-oz glass of 12% ABV wine and a 1.5-oz shot of 40% ABV spirits each contain about the same amount of pure alcohol. Total alcohol consumed, body weight, food and speed of drinking matter far more than the number on the label. If you choose to drink, pace yourself accordingly.
Why is the UK proof scale based on such an odd number?
The British scale grew out of the 18th-century gunpowder test: the weakest spirit that would still ignite soaked gunpowder was defined as 100 proof. When the scale was later formalised by measuring spirit density against a reference proof spirit, that anchor point worked out to exactly 57.06% ABV. That is why UK proof equals ABV × 7⁄4 rather than a round number like the US doubling.
Can a drink really be 200 proof?
No real beverage can. 200 US proof would be 100% pure ethanol, but ordinary distillation tops out around 95.6% ABV because ethanol and water form an azeotrope — they stop separating by simple boiling. Laboratory-grade absolute ethanol (99%+) requires chemical drying methods and is not sold as a drink. The strongest bottled spirits are grain alcohols around 190 US proof.