What is a fuel surcharge (FSC) in trucking?
A fuel surcharge (FSC) is the line on a trucking invoice that covers diesel costs above the fuel price already built into the line haul rate (the base rate for the main move). The line haul rate stays fixed; when diesel moves, the surcharge moves with it. Diesel can shift noticeably in a single week. For the week of September 21, 2026, the U.S. average was $6.529 a gallon, up $0.244 from $6.285 the week before. Billing fuel separately means neither side has to reprice the base rate every time that happens.
Many carriers tie the surcharge to the DOE/EIA weekly on-highway diesel price: the U.S. retail average, taxes included, that the Energy Information Administration posts every Tuesday around 10:00 a.m. ET based on Monday prices. After a federal holiday it comes out on Wednesday. EIA only publishes the price. It doesn't calculate, set or regulate fuel surcharges; the method is whatever the shipper and carrier agree to, and it varies by company and contract.
You'll run into two methods. Full truckload (FTL) surcharges are usually charged per mile: the gap between the current diesel price and the base price, divided by the truck's miles per gallon (MPG), times loaded miles. Less-than-truckload (LTL) carriers publish a fuel surcharge table that turns each diesel price band into a percentage of the line haul charge. Either way the index updates weekly, so the same lane at the same line haul rate can carry a different surcharge from one week to the next, and the surcharge on your quote may not be the one on your invoice.
How to calculate a fuel surcharge
Both methods start from the same number: the weekly diesel price named in your contract. What happens next depends on how the carrier bills.
For truckload, subtract the base fuel price (the diesel price already assumed in the line haul rate) from the current diesel price, divide by the truck's MPG to get the surcharge per mile, and multiply by loaded miles. For LTL, find the current diesel price in the carrier's fuel surcharge table, read off the percentage for that band, and apply it to the line haul charge.
Use the EIA weekly average the contract specifies, not the price at the pump where the driver fueled up. And because the index resets every week, check the week that applies to the shipment rather than the week you got the quote.
- Look up the DOE/EIA weekly on-highway diesel price. Use the U.S. average, or the regional (PADD) average if your contract names one. A single truck stop's price isn't the benchmark.
- Find the base fuel price and MPG in your rate agreement or the carrier's tariff. Figures like a $1.25 base or 6.0 MPG are common examples, but they're negotiated, not an industry standard.
- Truckload: subtract the base price from the current price, divide by MPG for the surcharge per mile, then multiply by loaded miles.
- LTL: take the percentage for the current price band from the carrier's fuel surcharge table and multiply the line haul charge by it.
- Recheck every week. EIA posts on Tuesday, and each carrier sets its own effective date; Estes, for example, applies the Tuesday price from the following Wednesday.
Fuel surcharge per mile: a worked example
Say a truckload contract sets the base fuel price at $1.25 a gallon and assumes 6.0 MPG, and this week's diesel average is $4.25. The run is 800 loaded miles. These are round numbers for illustration, not current prices.
| Current diesel (assumed) | $4.25/gal |
| Base fuel price | $1.25/gal |
| Price gap | $3.00/gal |
| Fuel economy | 6.0 MPG |
| Per mile ($3.00 ÷ 6.0) | $0.50/mi |
| Loaded miles | 800 mi |
| Total ($0.50 × 800) | $400.00 |
The fuel surcharge works out to $0.50 per mile, or $400.00 for the 800-mile run. That $400.00 is billed on top of the line haul rate, not inside it.
Per-mile vs. percentage fuel surcharges
Both methods read the same weekly diesel price; what differs is what the surcharge is charged against. The diesel index itself isn't a charge, just the reference price.
| Truckload (per mile) | LTL (percentage) | Diesel price index | |
|---|---|---|---|
| Charged on | Loaded miles | Line haul charge (Estes excludes accessorial charges) | Nothing; reference price only |
| Formula | (diesel − base) ÷ MPG × miles | Table % × line haul | Price → table band → % or $/mi |
| Inputs | Diesel, base price, MPG, miles | Diesel, carrier table, line haul | EIA weekly average |
| Updates | Weekly, with the index | Weekly, with the index | Posted Tuesday from Monday prices |
| Typical use | Full truckload, contract lanes | LTL freight | Both TL and LTL tables |
Common mistakes
- Comparing a truckload per-mile surcharge with an LTL percentage. One is charged on miles, the other on the line haul dollar amount, so there's no one-to-one conversion even at the same diesel price.
- Checking the surcharge against a local pump price. Surcharge formulas key off a weekly index (for many carriers, the EIA U.S. or regional average), so a truck stop receipt won't match.
- Treating the base fuel price as a fixed standard. It's a contract figure. A lower base means a bigger price gap and a higher surcharge; a higher base means more of the fuel swing is absorbed inside the line haul rate.
- Plugging in an optimistic MPG. The higher the MPG, the lower the surcharge per mile, so an inflated figure understates what you'll be billed.
- Reusing last week's surcharge. The index resets weekly, so the surcharge on the quote can differ from the one on the invoice even when the lane and line haul rate haven't changed.
What is FSC in trucking?
FSC stands for fuel surcharge: a separate invoice line that covers diesel costs above the base fuel price built into the line haul rate. The line haul rate stays fixed and the surcharge absorbs swings in the diesel price. EIA publishes the weekly diesel price many carriers use, but it doesn't calculate or regulate surcharges. Each carrier or contract sets its own method.
How do you calculate a fuel surcharge?
For truckload, subtract the base fuel price from the current diesel price, divide by the truck's MPG to get the surcharge per mile, then multiply by loaded miles. With assumed figures: ($4.25 − $1.25) ÷ 6.0 MPG = $0.50 per mile, and $0.50 × 800 miles = $400.00. LTL carriers work differently: they apply a percentage from their fuel surcharge table to the line haul charge.
How is an LTL fuel surcharge different from truckload?
An LTL carrier's fuel surcharge table matches the weekly EIA diesel average to a price band, and each band carries a percentage of the line haul charge: surcharge = line haul × percentage ÷ 100. Bands and percentages vary by carrier. Estes, for example, applies its percentage to net line haul only, not to accessorial charges. Because truckload is charged on miles and LTL on line haul dollars, there's no one-to-one conversion between them.
How often does the fuel surcharge change?
Weekly. EIA posts the U.S. on-highway diesel average every Tuesday around 10:00 a.m. ET, based on Monday prices, or on Wednesday after a federal holiday. Carriers set their own effective date; Estes, for example, applies the price posted Tuesday starting the following Wednesday. That's why the surcharge on a quote can differ from the one on the final invoice.
What is the base fuel price in a fuel surcharge?
The base fuel price is the diesel price already assumed in the line haul rate; the surcharge only covers what's above it. It's set in your rate agreement or the carrier's tariff. You'll sometimes see base prices of $1.25–$1.50 a gallon, but there's no published standard, so check the contract. A lower base means a bigger price gap and a higher surcharge. A higher base leaves more of the fuel swing inside the line haul rate.
What diesel price do carriers use to figure the fuel surcharge?
Many carriers use the DOE/EIA weekly U.S. average on-highway diesel price, which includes all taxes. EIA also publishes regional (PADD) averages, and some contracts name one of those instead. For the week of September 21, 2026, the U.S. average was $6.529 a gallon, the West Coast $7.456 and the Gulf Coast $6.177. The pump price at a particular truck stop isn't the contract benchmark.
Sources
All calculations run in your browser. Figures are based on published standards, carrier-published values and nominal dimensions, so check them against your carrier's own numbers before you book.
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