About the IFTA Fuel Tax Calculator
This IFTA calculator follows the International Fuel Tax Agreement method that interstate carriers use on their quarterly fuel tax return. List each US state or Canadian province you drove in with the miles travelled there, the tax-paid gallons you bought there and that jurisdiction’s fuel tax rate for the quarter. The calculator works out your fleet average MPG, the gallons you are deemed to have burned in each jurisdiction, and whether you owe tax or have a credit there — then nets everything into one figure payable to (or refundable by) your base jurisdiction.
It is meant for owner-operators and small fleets preparing returns, bookkeepers checking IFTA software output, and dispatchers estimating the fuel-tax effect of where drivers buy fuel. An optional late-filing section applies the IFTA penalty (the greater of $50 or 10% of tax due) and monthly interest at the U.S. IFTA rate, 9% a year for 2026.
Tax rates change every quarter and differ by fuel type, so take them from the IFTA tax rate matrix for the quarter you are reporting — the default rows use the 4th-quarter 2026 diesel rates for Texas ($0.20), Oklahoma ($0.19), Arkansas ($0.285) and Tennessee ($0.27). Surcharge jurisdictions (Kentucky and Virginia on the current matrix) are entered as an extra line whose name contains “surcharge”; those lines are taxed on the same miles but are kept out of the fleet MPG totals and get no tax-paid credit. This is an estimate; file the return through your base jurisdiction.
With the default inputs, the net tax due (− = credit) is $57.99. Change any value above to recalculate instantly.
How to use the ifta fuel tax calculator
- 1Total each jurisdiction’s miles from your trip sheets or ELD for the quarter.
- 2Total tax-paid gallons bought in each jurisdiction from fuel receipts.
- 3Look up each rate for the quarter and fuel type on the IFTA tax rate matrix.
- 4Enter one line per jurisdiction: name, miles, gallons, rate.
- 5Read the net tax due or credit; add months late if the return is overdue.
Formula and method
IFTA treats all of a carrier’s qualified vehicles of one fuel type as a fleet. The fleet average MPG is total miles in all jurisdictions divided by total gallons consumed, reported to two decimals. Each jurisdiction’s taxable miles divided by that MPG gives the gallons deemed burned there (rounded to whole gallons, as on the return).
Subtracting the tax-paid gallons bought in that jurisdiction gives net taxable gallons, which are multiplied by its tax rate. A positive result is tax owed; a negative result is a credit for tax already paid at the pump. The base jurisdiction nets all lines into one payment or refund. Late returns carry a penalty of $50 or 10% of delinquent tax, whichever is greater, plus interest that accrues monthly at 1/12 of the annual IFTA rate.
- MPG
- Fleet average miles per gallon for the quarter
- Taxable miles
- Miles in the jurisdiction subject to fuel tax
- Tax-paid gallons
- Fuel bought at retail in the jurisdiction with tax included
- Rate
- Jurisdiction fuel tax rate for the quarter and fuel type
Worked examples
Four-state quarter (4Q 2026 diesel rates)
29,500 miles ÷ 4,500 gallons = 6.56 MPG. Texas: 12,000 ÷ 6.56 = 1,829 taxable gallons − 1,500 paid = 329 × $0.20 = $65.80 owed. Oklahoma: 1,220 − 2,100 = −880 × $0.19 = $167.20 credit. Arkansas: 762 × $0.285 = $217.17 owed. Tennessee: 686 − 900 = −214 × $0.27 = $57.78 credit. Net: $57.99 due.
Same quarter filed two months late
The penalty is the greater of $50 or 10% of $57.99, so $50. Interest at 9% a year is 0.75% a month on the $282.97 owed to the jurisdictions with balances due: 282.97 × 0.0075 × 2 = $4.24. Total payable: $112.23.
Fuel bought mostly in high-tax states
20,000 miles ÷ 3,000 gallons = 6.67 MPG. Pennsylvania: 900 − 1,800 = −900 gallons × $0.741 = −$666.90. Ohio: 1,349 × $0.47 = $634.03. Indiana: 750 − 1,200 = −450 × $0.63 = −$283.50. Net credit $316.37 — buying fuel in high-tax states creates credits on the return.
Kentucky and Virginia with surcharge lines
Surcharge lines are left out of the totals, so MPG is 13,000 ÷ 2,000 = 6.5. Kentucky: 615 taxable gallons − 900 paid = −285 × $0.22 = −$62.70, but its surcharge applies to all 615 gallons × $0.105 = $64.58. Tennessee is a $47.79 credit; Virginia owes 462 × $0.336 = $155.23 plus a $66.07 surcharge. Net due: $175.39.
Frequently asked questions
How is IFTA fuel tax calculated?+
Divide total miles by total gallons to get fleet MPG. For each jurisdiction, divide its miles by MPG to get taxable gallons, subtract the tax-paid gallons you bought there and multiply by its tax rate. Positive results are owed, negative results are credits, and the total is paid to or refunded by your base jurisdiction.
When are IFTA returns due?+
Quarterly returns are due on the last day of the month after each quarter ends: April 30, July 31, October 31 and January 31. A return is required even if you did not operate, and late returns face a $50 minimum penalty plus interest.
Where do I find current IFTA tax rates?+
IFTA, Inc. publishes a tax rate matrix every quarter listing each member jurisdiction’s rate by fuel type, including surcharges, with US and Canadian figures. Use the rates for the quarter you are reporting, not the current pump price tax.
Who needs an IFTA license?+
Motor carriers operating qualified motor vehicles in two or more member jurisdictions — generally vehicles with two axles and over 26,000 lb gross vehicle weight, three or more axles, or a combination over 26,000 lb. Recreational vehicles are excluded.
How do I handle surcharge states like Kentucky or Virginia?+
Some jurisdictions, currently Kentucky and Virginia, levy a surcharge on taxable gallons that cannot be offset by fuel purchased there. Add a separate line with “surcharge” in its name, such as “Kentucky surcharge, 4500, 0, 0.105”, using the same miles and the surcharge rate from the matrix. The calculator leaves surcharge lines out of total miles and gallons so fleet MPG is not distorted.
What interest rate applies to late IFTA returns?+
For fleets based in a US jurisdiction the IFTA rate is the IRS underpayment rate plus two percentage points — 9% a year for 2026 — charged monthly at 1/12 of the annual rate on tax due to each jurisdiction.
Tax results are estimates based on published rules and simplified assumptions. They are not tax advice — check official guidance or a tax professional for your situation.