Montana Gas Tax Calculator
2026Montana charges 33.75¢ a gallon in state tax on gasoline and 30.5¢ on diesel in 2026, on top of the federal 18.4¢ and 24.4¢: 52.15¢ and 54.9¢ a gallon in all. Estimate your fuel costs.
By Konstantin Iakovlev · Updated October 19, 2026 · Methodology
Fuel Needed
1.0 gal
Trip Cost
$4.33
Annual Cost
$1,125.80
Fuel Cost Breakdown
| Total Distance | 30.0 miles |
| Fuel Needed | 1.00 gallons |
| One-Way Cost | $4.33 |
| Trip Cost | $4.33 |
| Weekly Cost | $21.65 |
| Monthly Cost | $93.82 |
| Annual Cost | $1,125.80 |
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.
Montana Gas Tax Overview
Montana’s state tax on gasoline is 33.75¢ a gallon and 30.5¢ on diesel, the rate in force since July 1, 2022. That is the 20th-highest state gasoline tax of the 50 states and DC. No automatic adjustment; the last scheduled increase took effect July 1, 2022.
With the federal 18.4¢, a gallon of gasoline carries 52.15¢ of per-gallon tax, so a 15-gallon fill-up includes about $7.82 of fuel tax whatever the pump price.
Montana Fuel Taxes (2026)
| State Gasoline Tax | 33.75¢/gal |
| State Diesel Tax | 30.5¢/gal |
| Federal Excise Tax | 18.4¢ gasoline / 24.4¢ diesel |
| Total per Gallon | 52.15¢ gasoline / 54.9¢ diesel |
| How the State Rate Is Built | Gasoline: 33¢ excise + 0.75¢ petroleum storage tank cleanup fee. Diesel: 29.75¢ excise + the same 0.75¢ fee. |
Official Sources: