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Montana Gas Tax Calculator

Montana charges 33.8¢/gal on gasoline and 30.5¢/gal on diesel (all state taxes and fees). Combined with the federal tax, drivers in Montana pay 52.3¢/gal total on gasoline. The base excise rate is 33.0¢/gal.

MN gasoline (combined)

33.8¢

excise: 33.0¢

MN diesel (combined)

30.5¢

excise: 29.8¢

Federal gasoline tax

18.5¢

18.4¢ excise + 0.1¢ LUST

Combined (gas + federal)

52.3¢

Includes excise + all state fees and surcharges (33.8¢/gal).

Federal gasoline excise18.4¢/gal
Federal LUST fee0.1¢/gal
Montana combined33.8¢/gal
↳ of which excise33.0¢/gal
Combined rate52.3¢/gal
Rates updated for June 2026

Tax on 15 gallons of gasoline in Montana(all fees)

Federal tax

$2.77

Montana tax

$5.06

Total tax

$7.84

This calculator is for informational purposes only and does not constitute tax advice. Consult a qualified tax professional for your specific situation. Rates last verified June 2026.

Verify rates on Montana Department of Transportation — Motor Fuel Tax Rates

Gas tax per fill-up in Montana

State column uses the combined rate (33.8¢/gal, all fees). Excise-only rate is 33.0¢/gal.

Tank sizeState taxFederal taxTotal tax
10 gallons$3.38$1.85$5.22
12 gallons$4.05$2.22$6.27
15 gallons$5.06$2.77$7.84
18 gallons$6.08$3.33$9.40
20 gallons$6.75$3.70$10.45
25 gallons$8.44$4.63$13.06
30 gallons$10.13$5.55$15.67

Gasoline only. State tax uses combined rate (all fees). Federal includes 18.4¢ excise + 0.1¢ LUST fee.

Montana note: Combined rate adds the state's petroleum tank release cleanup fund fee of 0.75 cents per gallon to the base statutory excise tax rates for both gasoline and special fuel (diesel).

Frequently asked questions

What is the gas tax in Montana?
Montana's state gasoline tax is 33.8¢ per gallon (all fees included; excise-only is 33.0¢) and the diesel tax is 30.5¢ per gallon (excise-only: 29.8¢). Combined with the federal 18.4¢/gal gasoline excise and 0.1¢/gal LUST fee, drivers in Montana pay a total of 52.3¢ per gallon of gasoline in state and federal taxes.
How much gas tax do I pay on a full tank in Montana?
On a 15-gallon fill-up with gasoline in Montana, you pay approximately $5.06 in state taxes (all fees) plus $2.77 in federal tax — a combined total of $7.84 in taxes per fill-up. Use the calculator above to adjust for your tank size.
What is the difference between Montana's excise tax and combined tax on fuel?
Montana's gasoline excise tax is 33.0¢/gal — this is the pure statutory per-gallon tax set by the state legislature. The combined rate of 33.8¢/gal includes the excise plus additional state-level fees such as environmental surcharges, petroleum storage tank fees, or sales tax components. The combined rate is what drivers effectively pay per gallon.
What is the federal gas tax in 2026?
The federal gasoline excise tax is 18.4 cents per gallon and has been unchanged since October 1, 1993. The federal diesel excise tax is 24.4 cents per gallon. An additional 0.1 cent per gallon Leaking Underground Storage Tank (LUST) fee also applies to both fuels, bringing the combined federal rate to 18.5 c/gal (gasoline) and 24.5 c/gal (diesel). These taxes fund the Highway Trust Fund for interstate highway maintenance and mass transit.
What is the difference between excise rate and combined rate?
The excise rate is the pure statutory per-gallon excise tax set by the state legislature. The combined rate is the total state-level tax burden per gallon as compiled by the EIA, including the excise tax plus environmental fees, petroleum storage tank fees, inspection fees, and in some states an applicable sales tax on fuel. For most states the difference is small (under 2 c/gal), but states like California, Indiana, Illinois, Vermont, and Washington D.C. show significant gaps because they layer sales taxes or large surcharges on top of the excise.
Which state has the highest gas tax?
California has the highest combined state gas tax at 70.9 cents per gallon as of January 1, 2026, per the EIA. This includes the excise tax plus the 2.25% sales tax on gasoline. California also has the highest combined diesel tax at 87.3 c/gal. Illinois (66.4 c/gal gasoline) and Washington (59.04 c/gal) rank second and third.

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