IFTA Fuel Tax Calculator
Enter your miles and fuel purchases by state. The calculator applies each state's current diesel rate and shows what you owe (or your credit) this quarter. Free and private — nothing is stored.
How the math works
Fleet MPG = total miles in every state ÷ total gallons purchased everywhere.
Taxable gallons per state = miles in that state ÷ fleet MPG — the fuel you burned there, regardless of where you bought it.
Net taxable gallons = taxable gallons − gallons purchased in that state. Positive means you owe that state; negative is a credit.
Tax per state = net gallons × that state's rate. Kentucky and Virginia also charge a surcharge on every gallon burned there, with no credit for purchases. The quarterly balance is the sum across all states.
Oregon collects through its own weight-mile program instead of IFTA — its rate is $0.00 here, but Oregon miles still count toward fleet MPG.
Frequently asked questions
How is IFTA tax calculated?
First find your fleet MPG: total miles in all states divided by total gallons purchased. For each state, divide the miles you ran there by your fleet MPG to get taxable gallons, subtract the gallons you actually bought in that state, and multiply the difference by that state’s tax rate. States where you bought more fuel than you burned generate a credit; the sum of every state is what you owe (or get back) for the quarter.
When are IFTA returns due in 2026?
IFTA is filed quarterly: April 30 (Q1, Jan–Mar), July 31 (Q2, Apr–Jun), November 2 (Q3, Jul–Sep, since Oct 31 falls on a weekend) and February 1, 2027 (Q4, Oct–Dec). File even for quarters with zero miles — skipping a return triggers penalties.
Why do Kentucky and Virginia cost extra?
Both states charge a surcharge on top of the regular fuel tax. The surcharge is billed on every gallon you burn in the state and cannot be offset by fuel purchases there. This calculator adds those surcharge lines automatically.
Why does Oregon show a $0.00 rate?
Oregon does not tax diesel through IFTA — it runs a separate weight-mile tax program that you file directly with the state. Miles driven in Oregon still count toward your fleet MPG, which is why you should still enter them.
Can buying cheap fuel in the wrong state increase my IFTA bill?
Yes. IFTA settles tax by where you burn fuel, not where you buy it. Buying in a low-tax state and burning the fuel in a high-tax state leaves the difference due at filing time. The smart comparison is pump price minus that state’s tax rate.