IFTA Calculator Quarterly Fuel Tax by State
Add each jurisdiction you ran in this quarter to estimate your total IFTA tax liability.
Rates shown are illustrative example rates for this demo calculator. Pull current quarterly rates from IFTA Inc. before filing.
| State | Taxable Gal. | Tax Owed |
|---|---|---|
| AL | 600.0 | $186.00 |
IFTA Rates by State
Jump to a state-specific IFTA guide.
IFTA: Formula, Benchmarks, and a Worked Example
IFTA filing exists because a truck buys fuel in one state but drives through many, and without a reporting system, states with high fuel taxes but low fuel sales within their borders would collect far less than the miles actually driven there would suggest. The math itself is straightforward once you see it laid out: your fleet's overall fuel efficiency gets applied to the miles driven in each jurisdiction to figure out how many gallons should be taxed where. Understanding that mechanism makes the quarterly filing process much less mysterious, even before you get into any single state's specific rate.
What IFTA Filing Actually Requires
The International Fuel Tax Agreement requires carriers running in more than one member jurisdiction to report total miles driven and fuel purchased each quarter, then settle up fuel tax based on where the miles were actually driven rather than where the fuel was actually bought. A carrier that buys most of its fuel in a low-tax state but drives significant miles through a high-tax state owes the difference to that high-tax state through the IFTA return, and a carrier that overpays fuel tax in a low-mileage state gets a credit back.
The Formula Behind the Calculation
The core number everything else depends on is fleet mpg for the quarter: total miles driven across all jurisdictions divided by total gallons of fuel purchased across all jurisdictions, regardless of where each gallon was actually bought. That single mpg figure gets applied uniformly to every jurisdiction you drove through.
For each individual jurisdiction, taxable gallons is that jurisdiction's miles divided by the fleet mpg, which estimates how many gallons of fuel were theoretically burned driving through that specific state or province. Tax owed for that jurisdiction is taxable gallons multiplied by that jurisdiction's specific per-gallon tax rate. Summing tax owed across every jurisdiction gives the total IFTA tax liability for the quarter.
Realistic Industry Benchmarks
State fuel tax rates vary enormously: Oregon charges no per-gallon diesel tax at all and instead uses a separate weight-mile tax system, while Pennsylvania's combined rate runs around 74 cents a gallon, among the highest in the country. Texas and Oklahoma both sit closer to 19 to 20 cents a gallon, while Illinois runs notably higher at roughly 61.5 cents once all components are combined, which shows how much a route through just a few different states can shift total tax owed even at identical mileage.
A Worked Example
Consider a quarter where a truck runs 1,200 miles in Texas, 800 miles in Oklahoma, and 500 miles in Illinois, for 2,500 total miles, and the driver buys 400 gallons of fuel across all three states combined during that period. Fleet mpg is 2,500 miles divided by 400 gallons, which is 6.25 mpg.
For Texas: 1,200 miles divided by 6.25 mpg is 192 taxable gallons, and at Texas's example rate of $0.20 a gallon, that's $38.40 owed. For Oklahoma: 800 miles divided by 6.25 mpg is 128 taxable gallons, and at Oklahoma's example rate of $0.19 a gallon, that's $24.32 owed. For Illinois: 500 miles divided by 6.25 mpg is 80 taxable gallons, and at Illinois's example rate of $0.615 a gallon, that's $49.20 owed.
Adding the three jurisdictions together, total taxable gallons across the quarter is 192 plus 128 plus 80, which comes to exactly 400, matching the 400 gallons actually purchased, since fleet mpg was built directly from those same two totals. Total tax owed across all three jurisdictions is $38.40 plus $24.32 plus $49.20, which is $111.92 for the quarter.
Why Fuel Purchase Location Doesn't Match Tax Owed Location
A driver who buys most of their fuel in a low-tax state like Oklahoma but drives significant miles through a high-tax state like Illinois will owe money to Illinois through their IFTA return, even though little or no fuel was actually purchased there. This is exactly the mismatch IFTA is designed to correct, redistributing tax revenue toward the states where the miles were actually driven rather than where the fuel happened to be pumped.
Common Mistakes With IFTA Reporting
The most common mistake is tracking miles by state accurately but being sloppy about total gallons purchased, since fleet mpg (and therefore every jurisdiction's taxable gallons) depends entirely on getting that total right. The second is forgetting to include odometer or GPS mileage from personal or non-taxable trips separately, which can distort the fleet mpg calculation if mixed in with commercial miles that should be reported.
Get More Out of the IFTA Calculator
Fleet Miles Drive Fleet Gallons, Not the Other Way Around
IFTA doesn't track exactly where each gallon was burned. It allocates your total fuel purchased across jurisdictions based on your fleet's overall mpg and the miles driven in each one.
Tax Rates Vary Enormously by State
Per-gallon diesel tax rates run from nothing in a state like Oregon, which uses a weight-mile tax instead, to well over 70 cents in a state like Pennsylvania.
One Base Jurisdiction, One Consolidated Return
Instead of filing separately with every state you drove through, IFTA lets you file one return with your base jurisdiction that settles up what's owed or refunded across all of them.
What Owner-Operators Say
“I used to think IFTA tracked exactly where I bought fuel. Once I understood it's really about miles driven versus fleet mpg, the quarterly numbers made a lot more sense.”
“Running through Illinois always adds more to my quarterly total than I expect given how few miles it actually is. Now I budget for it ahead of time instead of getting surprised.”