Every US state sets a per se limit of 0.08% BAC for drivers 21 and over, except Utah, which is 0.05%. Commercial drivers are held to 0.04% by federal regulation, and drivers under 21 face a zero-tolerance limit of 0.02% or lower in every state.

Driver Limit Set by
Adult (21+), 49 states and DC 0.08% State law, under a federal funding condition
Adult (21+) in Utah 0.05% The only state below 0.08%
Commercial driver (CDL) 0.04% Federal regulation, identical in every state
Under 21 0.02% or lower State law; 0.02% is the federal maximum, not a standard

Those numbers look like a coincidence of fifty legislatures agreeing. They are not. Understanding why they line up tells you exactly where the uniformity stops and where you actually need to check your own state.

Why 0.08% is the same everywhere

Drink-driving law is state law — there is no federal DUI statute for ordinary drivers. Congress got uniformity a different way: 23 U.S.C. § 163 conditions federal highway money on a state having a 0.08% per se law. States that did not comply lost a share of their apportionment, and all of them complied.

That has a consequence worth holding on to. The federal provision fixes the number, not the details. Everything else — what counts as a second offence, how long you lose your licence, whether a high reading is a separate crime or a sentencing factor — is written fifty-one different ways.

Why 0.02% keeps appearing for under-21 drivers

The same mechanism, a different section. 23 U.S.C. § 161 withholds 8% of a state's highway apportionment unless it treats an under-21 driver with a BAC of 0.02% or greater as driving under the influence.

So 0.02% is a federal ceiling, not a national standard. Every state must be at least that strict, and many states stop exactly there — which is why 0.02% fills so many comparison tables. But a state is free to go lower, and several do.

California is the example worth knowing, because it is the state most people look up and it is not 0.02%. Vehicle Code § 23136 makes it unlawful for a driver under 21 to drive with 0.01% or greater. A second section, § 23140, creates a further offence at 0.05% for the same age group. Any table showing California at 0.02% has printed the federal condition instead of California's law.

Commercial drivers: 0.04%, and it is federal

This one is often described as something "many states" do. It is not a state rule at all.

49 CFR § 382.201 states that no driver shall report for duty or remain on duty performing safety-sensitive functions with an alcohol concentration of 0.04 or greater, and that no employer who knows of it may let them. 49 CFR § 383.51 then makes 0.04 or greater while operating a commercial motor vehicle a disqualifying offence — one year for a first offence, three years if hazardous materials requiring placards were being transported, and a lifetime disqualification for a subsequent one. Refusing the test is treated the same way.

There is also a rule with no number in it that catches people out: § 382.207 prohibits performing safety-sensitive functions within four hours of using alcohol, whatever the reading.

Where the uniformity actually stops

Three things vary by state, and these are the ones worth checking locally rather than reading off any national table.

1. Sub-0.08 offences

Some states criminalise impaired driving below the per se limit as a lesser offence. Colorado's DWAI applies from 0.05%, and New York and West Virginia run comparable tiers. In those states "under 0.08" is not the same as "not an offence".

2. High-BAC thresholds, which are not one thing

Most states treat a high reading more seriously, but they do it in structurally different ways, so the numbers are not comparable even when they look it:

  • New York creates a separate offence — Aggravated DWI under VTL § 1192(2-a)(a), at 0.18% or more.
  • Texas raises the class of the same offence. Penal Code § 49.04(d) makes a first DWI a Class A misdemeanor at 0.15% or more, which doubles the ceilings to $4,000 and one year. Note what triggers it: the figure the specimen analysis showed, not your BAC while you were driving.
  • Florida keeps the offence and substitutes a harsher mandatory range. § 316.193(4) sets $1,000–$2,000 and up to nine months for a first conviction at 0.15% or more — and applies the identical tier to anyone carrying a passenger under 18, with no BAC element at all.
  • California does not create an offence at all. Vehicle Code § 23578 directs the court to treat 0.15% or more as "a special factor that may justify enhancing the penalties" — a sentencing consideration, applied at the judge's discretion.

Four states, four mechanisms — and three of them land on the same number. A separate charge, a heavier class of the same charge, a substituted penalty range and an argument available to a judge are not interchangeable, so a column reading 0.18, 0.15, 0.15, 0.15 tells you very little about what actually happens. This is the column where national tables disagree with each other, and with the statutes, more than any other.

3. Everything downstream of the reading

Fines, jail exposure, licence suspension length, ignition interlock rules and the lookback period for counting prior offences are all state law and differ substantially. These are also the figures most often quoted out of date, because they change more frequently than the limits do.

Check your own state

We maintain per-state pages with the limit data and the calculator on the same screen — California, Texas, Florida, New York and Utah, with more being added as each state's statute is checked rather than estimated.

Where we have not read a state's statute directly, we would rather say so than print a number. The federal figures above hold everywhere; the state-level detail is what you should confirm locally.

What the numbers do not tell you

Impairment does not begin at the legal limit. NHTSA's crash data shows fatal-crash risk climbing steeply well before 0.08%, which is the reasoning behind Utah's move to 0.05% and behind the National Transportation Safety Board's recommendation that other states follow.

The practical point is narrower than it sounds. Because the under-21 limit is effectively any measurable alcohol, and because sub-0.08 offences exist in several states, the gap between "one drink" and "a charge" is much smaller than the 0.08% headline suggests.

If you want an estimate for your own weight, sex and timing, our BAC calculator will give you one — as an approximation, never as permission to drive.

Official sources

Sources
  1. Lower BAC Limits - NHTSA https://www.nhtsa.gov/book/countermeasures-that-work/alcohol-impaired-driving/countermeasures/legislation-and-licensing/lower-bac-limits