Can I Drive? The Morning After Calculator

Enter what you drank and when you stopped. Get an honest estimate of when you're safe to drive. The answer is probably later than you think.

By Dave A Shaw - March 2026 - Free, no signup

About You

What Did You Drink?

When Did You Stop Drinking?

Your Alcohol Timeline

Dave's take: I used to do the "I feel fine" test on Saturday mornings. Turns out feeling fine and being under the limit are completely different things. After 4 pints on a Friday, you're probably not legal until lunchtime Saturday. Nobody tells you that.

Since switching to AF beer for weeknights (and most weekends honestly), the morning driving thing just... stopped being a problem. Sounds obvious when you say it out loud. I've been drinking IMPOSSIBREW mostly - their IPA actually tastes like something, and the L-theanine means Tuesday evenings still feel like a proper wind-down. Referral link if you want a tenner off.

Important: This calculator gives rough estimates only. It is NOT a substitute for a breathalyser test. Alcohol affects everyone differently depending on food intake, metabolism, medication, tiredness, and many other factors. The only way to be 100% certain you're safe to drive is to not drink at all, or wait significantly longer than any calculator suggests. When in doubt, don't drive. This tool uses the Widmark formula with standard NHS unit calculations. UK drink driving limit is 80mg per 100ml of blood (50mg in Scotland).

Common Questions

How long after drinking can I drive?

As a rough guide, it takes about 1 hour per unit of alcohol for your body to process it. A pint of 4.5% lager is about 2.5 units, so 3 pints would take roughly 7-8 hours to clear. But this varies hugely depending on your weight, sex, metabolism, and whether you've eaten. The only guaranteed safe option is to not drink at all before driving.

Can I drive the morning after drinking?

This is where most people get caught out. After a heavy night (6+ pints or equivalent), you could still be over the limit at lunchtime the next day. The NHS says alcohol takes about 1 hour per unit to leave your system, and there's nothing you can do to speed it up - coffee, cold showers, food, and sleep don't help your body process alcohol any faster.

What is the UK drink driving limit?

In England, Wales, and Northern Ireland the legal limit is 80 milligrams of alcohol per 100ml of blood (0.08 BAC). In Scotland, the limit is lower at 50mg per 100ml (0.05 BAC). There is no reliable way to know your exact blood alcohol level without a proper test, which is why the safest approach is to not drink at all if you plan to drive.

Does alcohol-free beer show on a breathalyser?

No. Alcohol-free beers (0.0% to 0.5% ABV) contain such tiny amounts of alcohol that they won't register on a breathalyser or affect your ability to drive. For context, a ripe banana contains roughly the same amount of alcohol as a 0.5% AF beer. You'd need to drink dozens in quick succession to register anything - and at that point you'd have bigger problems than a breathalyser.

How many units in a pint of beer?

A pint (568ml) of standard lager at 4.5% is about 2.5 units. A pint of stronger lager (5.2%) is closer to 3 units. A pint of session ale (3.8%) is about 2.2 units. The formula is: volume in ml x ABV% / 1000 = units. The NHS recommends no more than 14 units per week spread across 3 or more days.

Can I speed up how quickly alcohol leaves my system?

No. Nothing speeds up alcohol processing - not coffee, not water, not food, not exercise, not sleep, not cold showers. Your liver processes alcohol at a fixed rate of roughly one unit per hour, and there's no way to change that. The myths persist because coffee makes you feel more awake (but still drunk), and food before drinking slows absorption (but once it's absorbed, you're on the same clock).

More from Dave Reads

Your Drinking Week Report Card - get graded on your weekly drinking habits

Hangover Cost Calculator - what hangovers actually cost you per year

Parkrun Alcohol Calculator - how much drinking slows your 5K

I Quit Drinking for 10 Weeks - My Numbers

Every AF Beer in Tesco, Ranked