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Idaho Gas Tax Calculator

Idaho charges 32.0¢/gal on gasoline and 32.0¢/gal on diesel (all state taxes and fees). Combined with the federal tax, drivers in Idaho pay 50.5¢/gal total on gasoline.

ID gasoline (combined)

32.0¢

ID diesel (combined)

32.0¢

Federal gasoline tax

18.5¢

18.4¢ excise + 0.1¢ LUST

Combined (gas + federal)

50.5¢

Excise and combined rates are equal for Idaho — no separate fees apply.

Federal gasoline excise18.4¢/gal
Federal LUST fee0.1¢/gal
Idaho combined32.0¢/gal
Combined rate50.5¢/gal
Rates updated for June 2026

Tax on 15 gallons of gasoline in Idaho

Federal tax

$2.77

Idaho tax

$4.80

Total tax

$7.57

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 Idaho State Tax Commission — Fuel Distributors Tax Rate Table

Gas tax per fill-up in Idaho

Tank sizeState taxFederal taxTotal tax
10 gallons$3.20$1.85$5.05
12 gallons$3.84$2.22$6.06
15 gallons$4.80$2.77$7.58
18 gallons$5.76$3.33$9.09
20 gallons$6.40$3.70$10.10
25 gallons$8.00$4.63$12.63
30 gallons$9.60$5.55$15.15

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

Idaho note: State excise tax is a flat 32.0 c/gal for both gasoline and diesel. The state's 1-cent per gallon underground storage tank (UST) transfer fee triggers off or on dynamically depending on the state insurance fund's balance and is currently un-levied.

Frequently asked questions

What is the gas tax in Idaho?
Idaho's state gasoline tax is 32.0¢ per gallon (all fees included) and the diesel tax is 32.0¢ per gallon. Combined with the federal 18.4¢/gal gasoline excise and 0.1¢/gal LUST fee, drivers in Idaho pay a total of 50.5¢ per gallon of gasoline in state and federal taxes.
How much gas tax do I pay on a full tank in Idaho?
On a 15-gallon fill-up with gasoline in Idaho, you pay approximately $4.80 in state taxes (all fees) plus $2.77 in federal tax — a combined total of $7.58 in taxes per fill-up. Use the calculator above to adjust for your tank size.
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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