Fuel Surcharge Explained: How FSC Works and How to Calculate It
Fuel surcharges show up on almost every rate confirmation, but how they're calculated varies wildly. Here is how FSC actually works and how to make sure you're getting paid correctly.
May 21, 2026 · 7 min read
A fuel surcharge (FSC) is meant to offset the cost of diesel above a baseline price. When diesel climbs, your fuel costs climb, but the base linehaul rate you negotiated doesn't change automatically. The FSC is the mechanism that adjusts your pay to account for fuel volatility. Simple in concept. In practice, the way brokers and shippers calculate FSC varies enough that you can end up significantly under-compensated if you're not paying attention.
The two main FSC structures
Cents-per-mile FSC
The most straightforward structure: you get paid an additional set amount per loaded mile based on the current diesel price. For example, a broker might have an FSC table that says: diesel at $3.50 to $3.74 per gallon = $0.35/mile FSC, diesel at $3.75 to $3.99 = $0.42/mile FSC, and so on. The table shifts your total effective rate per mile as diesel moves.
Percentage-of-linehaul FSC
Some contracts, particularly with larger shippers, calculate FSC as a percentage of the base linehaul rate. If the base rate is $2.00/mile and the FSC is 18%, you receive $2.36/mile total. The percentage itself is usually indexed to a published diesel price, so it steps up or down as diesel moves.
What diesel price index is used
Most carriers and brokers in the US reference the DOE/EIA national average retail diesel price, published every Monday by the US Energy Information Administration. You can find it at eia.gov. Some shippers use a regional EIA index (like the Lower Atlantic or Midwest region) which can be higher or lower than the national average. Know which index applies to your contract so you can verify the math.
How to calculate FSC yourself
A common carrier-side FSC formula used by many fleets: FSC per mile = (Current diesel price - Baseline price) divided by baseline MPG.
For example, if current diesel is $3.90, the baseline is $1.20 (a common baseline used in many older carrier contracts), and your truck gets 6 miles per gallon: FSC = ($3.90 - $1.20) / 6 = $0.45 per mile. That's the fuel cost above baseline per mile at your fuel economy.
The problem: many broker FSC tables were designed with lower fuel baselines and older MPG assumptions. If diesel is at $3.90 and a broker is paying you $0.28/mile FSC based on an outdated table, you're absorbing fuel cost above that. When you negotiate with a new broker, ask to see their FSC schedule and make sure the baseline and step structure reflect current costs.
All-in rates and FSC
Many spot loads are offered as all-in rates with no separate FSC line. The broker has rolled fuel cost into the single rate you see. That's fine if the rate is sufficient. But it means when diesel spikes the following week, you have no FSC mechanism to trigger. Spot loads are exactly that, one-time. For contract freight, separating base rate and FSC gives both sides a cleaner structure when diesel moves.
Verifying you were paid the correct FSC
On any load with a separate FSC, your invoice should show the base linehaul rate and the FSC as separate line items. Check the broker's payment against the FSC table in your contract. Common discrepancies: broker used last week's diesel price instead of the rate con date, or the table step was applied at the wrong tier. These are usually honest mistakes, but they add up. Keep a record of the EIA diesel price for the week each load was booked.
Reefer fuel surcharge: a separate item
If you pull refrigerated freight, you may also have a reefer fuel surcharge separate from your truck's diesel FSC. The reefer unit burns fuel continuously and independently of your drive axle. Some shippers cover reefer fuel at a flat per-mile rate, others use a separate surcharge table, and some roll it into the load rate. Verify in your rate confirmation which structure applies so you're not discovering it at invoice time.
Rigbird logs the FSC on each load alongside the base rate so your invoices always show the split correctly and you can verify payments against your rate cons.
Start freeThe bottom line
FSC is not a bonus. It's a cost recovery mechanism, and it only works if the table was designed with realistic fuel baselines and your actual truck's fuel economy. Understand the index your contracts reference, keep your FSC tables current when you negotiate, and verify the math on every payment that includes a separate FSC line item. A few cents per mile underpaid across hundreds of loads adds up to real money by year end.
