Gas Tax Calculator
See how much state and federal gas tax you pay on a fill-up in any state.
How is gas tax calculated?
Every gallon of gas sold in the US carries two layers of tax: a federal excise tax of a flat 18.4 cents per gallon, and a state gas tax that varies widely — from around 15 cents per gallon in low-tax states to well over 60 cents per gallon in the highest-tax states. Some states also layer on additional fees (environmental fees, underground storage tank fees, local option taxes) that get folded into the "at the pump" rate.
Why do gas prices vary so much by state?
State gas tax is only one factor — distribution costs, state-specific fuel blend requirements (like California's cleaner-burning formulation), local competition, and proximity to refineries all affect the price at the pump. States with high gas taxes, like California, Pennsylvania, Illinois, and Washington, often also have other cost pressures that push prices even higher.
These are approximate combined state gas tax rates for estimation purposes — actual rates change periodically and can include additional local taxes not reflected here.
Frequently Asked Questions
What is the federal gas tax rate?
The federal gas tax is a flat 18.4 cents per gallon, applied nationwide on top of whatever state gas tax rate applies. It has not changed since 1993.
Which states have the highest gas tax?
California, Pennsylvania, Illinois, and Washington are typically among the states with the highest combined gas tax rates, often 50-70+ cents per gallon when state excise tax and additional fees are included.
Which states have the lowest gas tax?
Alaska, Mississippi, Missouri, and Oklahoma tend to have some of the lowest gas tax rates in the country, often in the 15-20 cents per gallon range.
Why is gas so expensive in California?
California combines one of the highest state gas taxes in the country with a required cleaner-burning fuel blend, cap-and-trade carbon costs, and limited in-state refining capacity — all of which push pump prices well above the national average.
How much tax do I pay on a full tank of gas?
It depends on your state's rate and how many gallons you buy. Use the calculator above with your state and gallons purchased to see the exact state tax, federal tax, and total tax paid on your fill-up.
What does gas tax money get used for?
Gas tax revenue primarily funds road and bridge construction and maintenance through federal and state highway trust funds, along with some public transit projects in many states.
Does gas tax change often?
State gas tax rates change more often than the federal rate — some states tie their rate to inflation or fuel prices and adjust annually, while the federal 18.4 cents per gallon rate has stayed fixed for decades.