Montana DUI Laws and Penalties

The consequences and definition of a Montana driving under the influence (DUI) conviction.

Updated 3/31/2021

In Montana, a person can get a DUI for driving or being in actual physical control of a vehicle:

  • with a blood alcohol concentration (BAC) of .08% or more
  • with a THC (the psychoactive ingredient in marijuana) level of 5 ng/ml or more, or
  • while under the influence of alcohol or any other drug which diminishes the person's ability to safely operate a vehicle.

Each of these prohibitions is actually considered a separate offense in Montana, and there are some slight differences between the penalties depending on the type of DUI.

Jail Time and Fines for Montana DUI Convictions

The minimum and maximum jail time and fines you'll face for a DUI conviction in Montana largely depend on how many prior convictions you have. Two DUIs in ten years will result in a second DUI, while three in a lifetime will be a third offense. Here are the possible jail sentences and fines for a first, second, and third DUI conviction.

1st offense

2nd offense

3rd offense

Jail Time

24 hours to 6 months

5 days to 1 year

30 days to 1 year


$600 to $1,000

$1,200 to $2,000

$2,500 to $5,000

License Suspension

6 months

1 year

1 year

Ignition Interlock Device (IID)

Period of probation

Period of probation

Period of probation

Substance abuse evaluation. All DUI offenders must complete an evaluation to determine what treatment, educational classes, or other programs might be warranted to treat the driver's possible substance abuse issues. The evaluation is generally considered by the judge, and the convicted motorist must complete all court-ordered treatments before license reinstatement.

Probationary license. The judge is permitted to grant the convicted motorist the usage of a probationary license. This license permits the holder to drive for certain purposes but requires the use of an IID. Depending on the circumstances, the driver might be required to complete a certain portion of the suspension before being eligible for a probationary license.

Forfeiture. For a second or subsequent DUI, the judge can order vehicles owned by the defendant to be forfeited—meaning the vehicles would be taken and sold at the benefit of the state.

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