IFTA Quarterly Calculator
For interstate carriers who want to know what they owe (or get back) before they sit down to file. Pick a quarter, enter miles and fuel by jurisdiction. The calculator does the per-state math, applies the Kentucky and Virginia surcharges, flags Oregon's weight-mile carve-out, and shows you the quarter total in real time.
Filing due
February 1, 2027
Total miles
0
Total fuel (gal)
0.00
MPG (calculated)
…
Jurisdictions
2
Add miles and fuel per jurisdiction to see your quarter total.
Pick a state, type your quarterly miles in that state, and the gallons of diesel you bought there. Repeat for every jurisdiction you ran in.
Dockex
The reason this calculator exists.
We built it for the moment a fleet manager realizes they have to do this exact math 4 times a year, forever. Dockex pulls per-jurisdiction miles directly from your ELD, tracks fuel receipts, applies the surcharges, runs this same arithmetic every quarter, and (for Oklahoma carriers) files the return for you. Outside Oklahoma, you get the ready-to-submit return for your base state.
If you run trucks across state lines and you're IFTA-licensed, you already know the quarterly drill: total your miles per jurisdiction, total your fuel per jurisdiction, divide miles by MPG, multiply by each state's rate, net against what you paid at the pump. Two states (Kentucky, Virginia) add a consumption-only surcharge on top. Oregon doesn't use the per-gallon system at all. The math itself is not hard, but doing it cold under a deadline, with a different rate per state and a surcharge in two of them, is where carriers leak money.
This calculator runs the same arithmetic the official return runs, against the current IFTA, Inc. matrix. Fleet MPG rounds to two decimals, gallons round to whole gallons, and the Kentucky and Virginia surcharges sit on their own lines — all three the way IFTA-101 does it, and the same way Dockex prices a real return. It is an estimator, not a filing tool. Use it before you file to see what the bottom line is going to look like, and to catch entry errors: if your miles and gallons imply an MPG a truck can't physically produce, it says so before you carry the number onto a return.
What the bottom number means
A positive total is the net fuel tax you owe across all jurisdictions for the quarter. It gets paid to your base state when you file, and your base state redistributes it to the others. It is net tax and nothing else — file late and penalty and interest land on top of it, and a credit carried in from a prior quarter comes off it.
A negative total is a net credit. You bought more fuel (and prepaid more tax) in high-rate states than your mileage there justified. Your base state credits the difference, and under IFTA Article R1120 that credit stays spendable against tax due for eight quarters before you have to claim it as a refund instead.
A per-state line going negative just means you overpaid that specific jurisdiction at the pump. That credit nets against states where you underpaid, which happens any time you drove somewhere you didn't fuel up.
A surcharge line never goes negative. Kentucky and Virginia charge theirs on the gallons you burned there and no pump ever collects it, so there is nothing to credit back — which is why it sits on its own line instead of inside that state's net.
If the number looks crazy, MPG is usually the culprit. Real Class 8 fleet MPG sits between 5.5 and 7.5. The calculator flags outside-band MPG automatically, so check the warning before you trust the total.
How IFTA actually works
IFTA (the International Fuel Tax Agreement) exists because trucks burn fuel in one state and pay tax in another. Before IFTA, carriers had to file fuel tax returns in every state they drove through. The agreement collapses that into one quarterly return filed with your base state, which redistributes the money to every other member jurisdiction.
You buy fuel anywhere, and the per-gallon fuel tax baked into the pump price stays with the state that sold it to you. At the end of the quarter, you reconcile: how much fuel did you actually burn in each jurisdiction (based on miles driven and fleet MPG), and how much tax did you prepay at the pump there? The difference is what you owe or get back.
IFTA returns are due 4 times a year: April 30, July 31, October 31, and January 31 (Q1 through Q4 in that order). When one of those lands on a weekend or a federal holiday it moves to the next business day — Q3 2026 is due Monday November 2, not Saturday October 31 — which is why the date in the calculator header sometimes differs from the one on the statute. Late filings carry a $50 minimum penalty plus interest, and the bigger risk is that a late or short filing flags you for audit. Audits cover 4 years and demand trip-level mileage and fuel receipts.
The detailed filing walkthrough lives in our blog post: IFTA Quarterly Filing Walkthrough.
Frequently asked
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