IFTA Fuel Tax Calculator

No -- treat it strictly as an illustrative example, not a published rate for any specific state or province. IFTA member jurisdictions set their own fuel tax rates and publish an updated matrix every quarter, with real rates in recent history ranging from roughly $0.18/gal to over $1.00/gal depending on jurisdiction and fuel type. Always look up the actual current-quarter rate from the official IFTA tax rate matrix before using this calculator for a real filing.

Tax Owed goes negative whenever Gallons Purchased Here (Credit Gallons) exceeds Taxable Gallons -- meaning you bought and already paid tax on more fuel in that jurisdiction than your mileage-based apportionment says you actually owe tax on there. IFTA is designed so jurisdictions where you over-bought fuel relative to miles driven generate a credit that offsets what you owe in jurisdictions where you under-bought relative to miles driven. Note that Tax Rate's effect on Tax Owed flips sign once you're in this credit position: with a normal (positive) Net Taxable Gallons, a higher Tax Rate increases the amount owed, but with a negative Net Taxable Gallons, a higher Tax Rate instead increases the size of the credit -- Tax Owed becomes more negative, not less.

No -- Tax Owed is calculated purely from this jurisdiction's own Net Taxable Gallons and Tax Rate; Number of Jurisdictions only multiplies that single-jurisdiction figure to produce Est. Total Liability, a rough same-rate-everywhere estimate across your whole operation. A real IFTA return calculates each jurisdiction separately with its own actual tax rate and mileage share, which this rough multiplier does not replicate.

This calculator's input ranges allow it, but the result won't make physical sense -- Jurisdiction Miles is supposed to be a subset of Total Miles (All Jurisdictions), so entering more miles for one jurisdiction than you drove in total will push Taxable Gallons above what your fleet actually purchased. Double-check that Jurisdiction Miles never exceeds Total Miles before relying on the result.

Fleet MPG itself (Total Miles divided by Total Gallons) is shown for reference, but Taxable Gallons is computed directly from the ratio of Jurisdiction Miles to Total Miles applied to Total Gallons Purchased, which amounts to the same fuel-efficiency assumption without a separate MPG step. A lower Fleet MPG (more fuel burned per mile) means more gallons apportioned to every jurisdiction you drove through, this one included.