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how many units of alcohol can you drive on

You cannot reliably “count units” and know you are safe or legal to drive. Even small amounts of alcohol can impair you, and the only truly safe number is zero.

Key legal limits (UK context)

In the UK, the law is written in terms of alcohol in your body, not units you drank:

  • England, Wales, Northern Ireland:
    • 35 micrograms of alcohol per 100 ml of breath
    • 80 milligrams of alcohol per 100 ml of blood
    • 107 milligrams of alcohol per 100 ml of urine
  • Scotland (stricter):
    • 22 micrograms of alcohol per 100 ml of breath
    • 50 milligrams of alcohol per 100 ml of blood
    • 67 milligrams of alcohol per 100 ml of urine

These limits are not “targets” and don’t translate neatly into a fixed number of units for everyone.

“How many units can I drive on?”

Rough, very general guidance sometimes quoted:

  • Men: about 2–3 (sometimes 3–4) units can already be close to or over the limit for some people.
  • Women: about 1–2 units can be enough to be close to or over the limit.

But this is highly variable and can be wrong for you because it depends on:

  • Body weight and sex
  • How quickly you drank
  • Strength and size of the drinks
  • Food in your stomach
  • Metabolism, health, tiredness, medications

Two people drinking the “same” number of units can end up on opposite sides of the legal limit.

Why “just one or two is fine” is risky

  • “I feel fine” does not equal “I’m under the legal limit.” Reaction time and judgment are affected before you feel drunk.
  • Pub rules like “a pint or two is fine” are outdated and can easily leave you over the limit.
  • Counting units is not a safe decision tool because drink sizes, ABV, and your body all change.

A lot of safety campaigns and insurers now push the message: if you are driving, don’t drink at all.

Morning after and leftover alcohol

Even if you stopped drinking the night before:

  • Your body only clears alcohol slowly over several hours.
  • You can still be over the limit the next morning after heavy or late drinking, even if you “feel OK.”

Many drink‑driving arrests now happen in the morning for exactly this reason.

Practical takeaway

For the exact question “how many units of alcohol can you drive on”:

  • There is no fixed safe number of units that guarantees you are legal or safe to drive.
  • Legal limits are set in breath/blood/urine levels, and converting that to “units” is too unreliable person‑to‑person.
  • The safest and most responsible choice if you plan to drive is: no alcohol at all.

Bottom line: If you’re driving (or might need to drive), treat 0 units as the only dependable answer.

TL;DR: You can’t safely use units to know you’re legally OK to drive; even 1–2 units can put some people over the limit. Zero alcohol is the only reliably safe driving choice.

Information gathered from public forums or data available on the internet and portrayed here.