Truck stop signs show pump prices, and the cheapest one looks like the obvious place to fill up. For a carrier filing IFTA it often isn't. This where-to-fuel calculator takes each state's diesel tax out of the pump price and shows what a gallon really costs you in each state on the route.
How it is calculated
Under the International Fuel Tax Agreement, the tax you owe a state depends on the miles you drive there, not on where you bought the fuel. The tax you paid at the pump is credited on your quarterly return. So for each state:
- Real cost of a gallon = pump price − that state's IFTA diesel tax rate
- Cheapest state = the lowest real cost
- Saving = (highest real cost − lowest real cost) × gallons you'll buy
Tax rates come from the IFTA tax matrix for the 4th quarter of 2026, with Kentucky's and Virginia's surcharges included. Pump prices are yours: new states start at the U.S. weekly average from the EIA until you type what you see.
A worked example
- Ohio: $6.40 pump − $0.470 tax
- $5.930
- Indiana: $6.50 − $0.630
- $5.870
- Pennsylvania: $6.60 − $0.741
- $5.859
- Illinois: $6.70 − $0.738
- $5.962
Ohio has the lowest pump price on this route, yet Pennsylvania is the cheapest fuel after IFTA, because more of its pump price is tax you get back. The pump prices here are examples; real ones move daily.
IFTA fuel tax by state: the highest and lowest
| Higher diesel tax, 4Q 2026 | $/gal | Lower diesel tax, 4Q 2026 | $/gal |
|---|---|---|---|
| California | 0.979 | Oklahoma | 0.190 |
| Pennsylvania | 0.741 | Louisiana | 0.200 |
| Illinois | 0.738 | Texas | 0.200 |
| Indiana | 0.630 | New Mexico | 0.210 |
| Washington | 0.595 | Delaware | 0.220 |
A high-tax state with a high pump price can be a fine place to buy. A low-tax state with a high pump price often isn't.
Where to get fuel, in practice
- Compare the states you'll actually pass through, with prices from the stops on your route.
- Fuel card discounts change the pump price; enter the price after your discount.
- Keep every receipt; the IFTA return needs them. The IFTA mileage and fuel log helps.
The trip's total fuel bill is in the trip fuel cost calculator, and how fuel prices flow into what loads pay in the fuel surcharge calculator. Reefer fuel is a separate question, covered in reefer units, and rates for power only in power only rates per mile. What dispatch costs is on dispatch cost.
Results are estimates. Rates change every quarter; check the IFTA matrix before you file.
SOURCES
- IFTA, Inc.: IFTA tax rate matrix: quarterly fuel tax rates for every member jurisdiction (checked 2026-10)
- IFTA, Inc.: IFTA Articles of Agreement, Procedures Manual and Audit Manual: fleet MPG, taxable gallons and record-keeping rules (checked 2026-10)
- U.S. Energy Information Administration: Weekly U.S. retail on-highway diesel: $6.382/gal for the week of Sept 28, 2026 (year ago $2.628 lower) (checked 2026-10)