Montana Gas Tax Calculator
2026Calculate total gas tax per gallon in Montana, including the federal excise tax of $0.184/gal and MT state fuel taxes. Compare Montana gas and diesel tax rates for 2026.
Written and reviewed by Konstantin Iakovlev · Methodology · Updated
Fuel Needed
1.0 gal
Trip Cost
$4.10
Annual Cost
$1,066.00
Fuel Cost Breakdown
| Total Distance | 30.0 miles |
| Fuel Needed | 1.00 gallons |
| One-Way Cost | $4.10 |
| Trip Cost | $4.10 |
| Weekly Cost | $20.50 |
| Monthly Cost | $88.77 |
| Annual Cost | $1,066.00 |
Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.
How much is gas tax in Montana?
Every gallon of gasoline pumped in Montana carries two layers of tax: a federal excise tax of 18.4¢ per gallon (24.4¢ for diesel) collected by the IRS, and a state-level fuel tax of approximately 33¢ per gallon that funds Montana highway, bridge, and transit projects. Combined, that's roughly 51.4¢ per gallon in 2026.
State gas tax rates vary widely — from under 10¢/gal in Alaska to nearly 60¢/gal in California and Pennsylvania. Some states, including Montana, periodically adjust the rate via fuel-index formulas tied to wholesale prices or inflation, so the figure can drift mid-year. Many states also stack on smaller environmental, underground-storage-tank, or pre-paid sales-tax fees that aren't always shown at the pump but are baked into the posted price.
For a typical 12-gallon fillup in Montana, you contribute about $6.17 to combined road and federal infrastructure funds before any sales tax. Use the calculator above with your local pump price and tank capacity for an exact breakdown of pre-tax fuel cost vs. tax burden.
Montana fuel-tax history, indexing, and where the money goes
- Diesel state tax (2026)
- 29.55¢ per gallon
- Last increase
- 2023 (final 2¢ step under HB 473 of 2017)
- Indexed?
- No — fixed until legislative action
- Where revenue goes
- Highways Special Revenue Account (constitutionally protected)
Montana raised its gas tax from 27.75¢ to 33¢ over 2017–2023 under the BRIDGE Act (HB 473), a 6¢ phased increase. The Highways Special Revenue Account is constitutionally protected and funds MDT capacity work, county and city street grants, and the Montana Highway Patrol. Montana has no statewide EV surcharge as of 2026 — the legislature debated HB 60 in 2023 but it failed. The state's vast road network is supported by relatively high fuel taxes per capita.
Montana Tax Rates (2026)
| Federal Gas Tax | $0.184/gal |
| State Sales Tax | 0% |
| State Income Tax | progressive (up to 5.7%) |
| Avg. Property Tax Rate | 0.74% |
Gas tax — frequently asked questions
What is the federal gas tax in 2026?
The federal motor fuel excise tax is 18.4¢ per gallon on gasoline and 24.4¢ per gallon on diesel. The federal rate has been unchanged since 1993; only state and local taxes have moved. Federal revenue funds the Highway Trust Fund, which finances most interstate and bridge maintenance.
How much is gas tax by state?
State gas tax rates range from about 9¢/gal in Alaska to roughly 58¢/gal in California and Pennsylvania (the two highest). Washington (~49¢), New Jersey (~42¢), and Illinois (~47¢) round out the higher tier. Most states layer 20–40¢/gal of state tax on top of the 18.4¢ federal rate. Some states index gas tax to inflation; others raise it via legislation as needed.
Why does gas cost more at the pump than the rate suggests?
The pump price reflects crude oil cost, refining margin, distribution and retail markup, plus combined federal + state + local taxes. In high-tax states like California, taxes alone account for ~70¢/gallon. EV-charging stations are taxed differently (often by kWh, sometimes via a separate registration surcharge).
Are gas taxes deductible?
Gas taxes are not deductible on personal federal returns. Self-employed drivers using actual vehicle expenses can include fuel costs in business deductions, but the cleaner method is the IRS standard mileage rate ($0.70/mile in 2026), which already bundles fuel, depreciation, and maintenance.
Has gas tax changed in 2026?
Several states adjusted gas taxes in 2026 (most are inflation-indexed and reset at the start of the calendar year or fiscal year). Federal rates remain at 18.4¢/24.4¢ — unchanged since 1993. Many states are also adding EV registration fees ($100–$200/year) to recoup lost gas-tax revenue as electric vehicles displace combustion engines.