IFTA Fuel Tax Calculator
Calculate fleet MPG and net taxable gallons for IFTA reporting
Frequently Asked Questions
First find your fleet MPG (total miles ÷ total gallons purchased across all jurisdictions). Then for each state, divide the miles driven there by your fleet MPG to get gallons consumed. Subtract the gallons you actually purchased in that state to get net taxable gallons, then multiply by that state's tax rate.
It means you purchased more fuel in that state than the miles driven there account for — that state owes you a credit rather than you owing tax, since you've effectively prepaid more fuel tax than your usage in that jurisdiction.
IFTA tax rates change quarterly and vary by jurisdiction and fuel type. Enter the current rate from your IFTA quarterly tax rate matrix for accurate results — using a stale rate is a common filing error.
No, this calculates the core numbers for one jurisdiction to help you understand and check your math. Your full quarterly return needs this calculation repeated for every jurisdiction you operated in, filed through your base state.
The 4-step IFTA formula
1) Fleet MPG = total miles ÷ total gallons purchased. 2) Gallons consumed in state = state miles ÷ fleet MPG. 3) Net taxable gallons = gallons consumed − gallons purchased in that state. 4) Tax owed = net taxable gallons × state tax rate. A negative result is a credit, not a charge.