Tax & Paycheck Calculators
IFTA Fuel Tax Calculator
The exact 4-step formula behind every quarterly IFTA return — fleet MPG, gallons consumed per jurisdiction, and what you owe or get credited, all in one place.
Calculate your quarterly IFTA tax
Add each jurisdiction you drove through this quarter — up to 4 shown, the math extends to as many as you need.
| Jurisdiction | Gal. consumed | Net taxable gal. | Tax owed / credit |
|---|
Fleet MPG: 0 — computed from total miles ÷ total gallons across all jurisdictions entered. Tax rates change quarterly and vary by fuel type — verify current rates at iftach.org before filing. Doesn't model per-jurisdiction surcharges (e.g., Kentucky, Virginia), which apply only to gallons consumed with no credit for tax-paid gallons.
The official 4-step IFTA formula
Every quarterly IFTA return, regardless of software or state portal, runs the same underlying calculation:
- Fleet MPG = Total miles driven (all jurisdictions) ÷ Total gallons purchased (all jurisdictions)
- Gallons consumed per jurisdiction = Miles driven in that jurisdiction ÷ Fleet MPG
- Net taxable gallons = Gallons consumed − Gallons actually purchased in that jurisdiction
- Tax owed or credit = Net taxable gallons × that jurisdiction's current tax rate
The logic behind step 3 is what makes IFTA fair across jurisdictions: if you bought more fuel in a state than your mileage there would suggest you burned, you get a credit in that state (you paid tax there on fuel you actually used elsewhere). If you drove a lot of miles in a state but didn't buy much fuel there, you owe additional tax to that state.
Who needs to file IFTA
- Vehicles with a gross vehicle weight over 26,000 pounds, or vehicles with three or more axles regardless of weight.
- Operating in two or more IFTA member jurisdictions.
- Used for commercial purposes — a personal-use RV or camper generally doesn't qualify.
Alaska, Hawaii, and Washington DC are not IFTA jurisdictions in the US, and the Canadian territories (Yukon, Northwest Territories, Nunavut) and all of Mexico aren't either — miles driven there are reported as non-IFTA miles and aren't part of the per-jurisdiction tax calculation, though they're still included in your fleet MPG.
Filing deadlines
| Quarter | Period | Due date |
|---|---|---|
| Q1 | Jan – Mar | April 30 |
| Q2 | Apr – Jun | July 31 |
| Q3 | Jul – Sep | October 31 |
| Q4 | Oct – Dec | January 31 |
Late filings carry a penalty of $50 or 10% of the net tax due, whichever is greater, plus roughly 1% interest per month on unpaid tax.
Watch for surcharge states
IFTA calculation formula verified against multiple independent trucking-industry IFTA calculators and guides, all describing the identical 4-step method. Filing deadlines and penalty structure cross-confirmed across sources. Tax rates change quarterly — always verify current per-jurisdiction rates at iftach.org before filing your actual return.
Frequently asked questions
Before you file your quarterly IFTA return.
How is IFTA fuel tax calculated?
Calculate your fleet's average MPG (total miles ÷ total gallons), then for each jurisdiction: divide the miles driven there by your fleet MPG to get gallons consumed, subtract gallons actually purchased there to get net taxable gallons, then multiply by that jurisdiction's tax rate.
What vehicles need to file IFTA?
Commercial vehicles with a gross vehicle weight over 26,000 pounds, or three or more axles regardless of weight, operating in two or more IFTA member jurisdictions.
Why would a state owe me a credit instead of me owing tax?
If you purchased more fuel in a jurisdiction than your mileage there would account for, you already paid more tax to that jurisdiction than you actually used — IFTA credits you the difference, which offsets tax owed to other jurisdictions.
When are IFTA returns due?
Quarterly: April 30 for Q1, July 31 for Q2, October 31 for Q3, and January 31 for Q4. Late filing carries a penalty of $50 or 10% of net tax due, whichever is greater, plus monthly interest.
Do I need to report miles driven in Alaska, Hawaii, or Mexico?
Those are non-IFTA jurisdictions, along with Washington DC and Canada's northern territories. Miles there are reported separately as non-IFTA miles and aren't part of the per-jurisdiction tax redistribution, though they still count toward your fleet MPG calculation.