In New Jersey, most DWI convictions require an ignition interlock device on your car — including most first offenses. How long it stays installed depends on your offense number and BAC: 3 months for BAC 0.08–0.099, 7–12 months for BAC 0.10–0.149, 12–15 months for BAC 0.15 or higher, and 2–4 years for second and third offenses. Refusing the breath test is a separate offense with its own interlock requirement. Answer a few questions below for a personalized timeline estimate.
An ignition interlock device (IID) is a breathalyzer wired into your car’s ignition. You blow into it before the engine starts, and periodically while driving. If it detects alcohol, the car won’t start — and the violation gets reported. In New Jersey, the interlock isn’t optional for most DWI convictions. It’s built into the sentence.
NJ DWI Interlock & License Timeline Calculator
See what a New Jersey DWI conviction can carry — license suspension, ignition interlock, fines, and more — mapped on a timeline.
How many prior DWI convictions do you have in New Jersey?
Count only prior convictions, not arrests or dismissed charges.
How long ago was your most recent prior DWI conviction?
New Jersey's 10-year "step-down" rule can reduce your sentence if enough time has passed.
What was the BAC reading?
Penalties for a first offense depend on BAC tier. (For repeat offenses, BAC doesn't change the penalties.)
Did you refuse the breath test?
Refusal is a separate charge (N.J.S.A. 39:4-50.4a) with its own penalties on top of the DWI.
How many prior refusal convictions do you have?
Refusal priors are counted separately from DWI priors.
Assumed sentencing date (optional)
We'll map your timeline from this date. Defaults to today.
Your estimated timeline & penalties
General information only — not legal advice. Penalties depend on the facts, your record, the court, and the judge's discretion within statutory ranges. Every one of these penalties can potentially be challenged. No attorney-client relationship is created by using this tool.
Charged with DWI in New Jersey?
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Who has to install one?
Almost everyone convicted of DWI in New Jersey. Since the 2019 law change, judges order interlocks for most first offenses — not just repeat offenders. Second and third offenses always carry interlock requirements. Refusing to take the breath test is a separate offense under N.J.S.A. 39:4-50.4a, and it comes with its own interlock period on top of any DWI interlock.
Charged with DWI? See our New Jersey DWI lawyer page for defense strategies and penalty information.
There is one important timing rule that can help: drivers who install an interlock voluntarily before conviction can earn credit that shortens the license forfeiture period. That’s a decision to make early, not after sentencing.
How long does it stay on?
It depends on two things: which offense number this is for you, and your BAC reading.
- First offense, BAC 0.08–0.099: license suspension or interlock — typically 3 months of interlock driving.
- First offense, BAC 0.10–0.149: license suspension or interlock — typically 7–12 months of interlock driving.
- First offense, BAC 0.15 or higher: mandatory 3-month license suspension (no driving at all), then typically 12–15 months of interlock driving.
- Second offense: interlock typically runs 2–4 years.
- Third offense: interlock typically runs 2–4 years.
If you were also convicted of refusal, that adds a separate consecutive interlock period. And there’s the 10-year step-down rule: if your prior DWI conviction was more than 10 years ago, you may be sentenced as a first offender — which can dramatically shorten everything. Old convictions can sometimes be challenged under State v. Laurick, so a prior on your record isn’t always the final word.
What does it cost, and what counts as a violation?
You pay for everything: installation (usually a few hundred dollars), monthly monitoring fees for the life of the device, and removal at the end. Miss a service appointment, fail a rolling retest, or try to start the car after drinking, and the device logs it. Violations can extend your interlock period and, in serious cases, bring new charges.
The tool above gives you your timeline
The calculator walks through your offense number, BAC tier, prior-conviction timing, and any refusal charge, then lays out your license forfeiture and interlock phases month by month — including fine ranges, IDRC requirements, and MVC surcharges. It’s an estimate based on the statutes, not a prediction of what a judge will do. For what the law means in your case, talk to a lawyer. Call (732) 303-7341 for a free consultation.
Will this stay on your record? Check New Jersey expungement eligibility.
For 0.08–0.099, expect license suspension or 3 months of interlock; for 0.10–0.149, suspension or 7–12 months of interlock; at 0.15 or above, a mandatory 3-month suspension plus 12–15 months of interlock. A lawyer can confirm which tier your reading falls into.
Only in a vehicle equipped with the interlock. Driving any vehicle without one during the interlock period is a separate violation.
Refusal is a separate offense with its own penalties, including its own interlock period that runs after the DWI interlock. So yes — a refusal conviction on top of a DWI conviction extends the total time.
The device logs the failure and reports it. Depending on the circumstances, a violation can extend your interlock period or lead to additional penalties. Repeated violations are treated seriously by the courts.
Drivers pay installation, a monthly monitoring fee for every month the device is installed, and a removal fee at the end. Costs vary by provider — get quotes from state-approved vendors.
Yes. New Jersey allows credit toward the forfeiture period for drivers who voluntarily install an interlock before conviction. This is a strategic decision worth discussing with your attorney early in the case.
General information only — not legal advice.
