What is Idaho's gas tax rate?

Idaho levies a state gasoline excise tax of 32 cents per gallon, one of the higher rates in the Mountain West. There is also a small transfer fee on each gallon. The state rate is added to the 18.4-cent federal gasoline excise that applies nationwide.

How much total tax is in a gallon of Idaho gas?

Combining Idaho's 32-cent state excise with the 18.4-cent federal excise, you pay about 50.4 cents of fuel tax per gallon, before any local fees. The pump price also includes the wholesale cost and retailer margin, which are not taxes.

Does Idaho charge sales tax on gasoline?

No. Idaho's gasoline excise is a fixed per-gallon amount and the state does not also apply its 6% general sales tax to motor fuel at the pump. The excise tax funds road and highway maintenance through the state highway account.

Is diesel taxed differently in Idaho?

Idaho taxes special fuels such as diesel at the same 32-cent-per-gallon state rate as gasoline, but the federal excise on diesel is higher at 24.4 cents per gallon. This calculator uses the gasoline figures; adjust the federal rate if you are computing diesel.

Why estimate gas tax per mile?

Per-mile gas tax shows the road-funding cost of your driving. Dividing the combined per-gallon excise by your fuel economy gives cents of tax per mile, which is useful for comparing vehicles and understanding how fuel-efficient cars pay less per mile into road funds.

Idaho Gas Tax Calculator

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Idaho charges a 32-cent-per-gallon state gasoline excise tax, one of the higher rates in the region, on top of the 18.4-cent federal excise — roughly 50.4 cents of tax in every gallon. Idaho does not also apply its 6% sales tax to fuel. This tool totals your gas tax per fill-up or across a year of driving.

How it works

Multiply the gallons you buy by the combined per-gallon excise. In annual mode, gallons come from your mileage divided by fuel economy:

combined excise = $0.324 (state, incl. transfer fee) + $0.184 (federal)
per fill-up     = tank gallons × combined excise
annual gallons  = annual miles ÷ miles per gallon
annual tax      = annual gallons × combined excise
per mile        = combined excise ÷ miles per gallon

A more fuel-efficient car burns fewer gallons, so it pays less excise per mile even though the per-gallon rate is the same for everyone.

Example and notes

A 15-gallon fill-up costs 15 × 0.508 = 7.62 dollars in fuel tax. Driving 12,000 miles a year at 25 mpg means 12,000 ÷ 25 = 480 gallons, or 480 × 0.508 = 243.84 dollars of gas tax annually, about 2.0 cents per mile. Diesel uses the same 32-cent state rate but a higher 24.4-cent federal rate. These are estimates using published rates; confirm the current figures with the Idaho State Tax Commission and the IRS.