Guide
Fuel surcharge: how to read the schedule and check the math
A fuel surcharge is meant to cover the part of fuel cost that moves after the rate was set. Whether it does depends on three numbers in the schedule and the miles it is paid on. You can check all three on one load.
In short
- Most schedules reduce to one formula: (current diesel price − base price) ÷ peg miles per gallon = surcharge per mile.
- Check which miles it pays on. Many pay loaded miles only, while your truck burns fuel on empty miles too.
- Your actual mpg is rarely the schedule’s peg mpg. The gap is a small loss on every load.
- Read the schedule and its index source in the rate con or tariff. This guide cannot see your contract.
The formula, with a price line
Take a schedule with a base price of $3.60 per gallon and a peg of 6.0 mpg. Both are invented. At $3.60 the surcharge is zero. Each dollar the index rises adds 1 ÷ 6 = $0.1667 per mile.
The chart shows the per-mile surcharge at five invented index prices. The line is straight, which is why one load is enough to test your schedule.
The index is usually a published weekly price. For context, the EIA U.S. retail diesel average was $6.199 per gallon for the week of Oct 5, 2026 (EIA API weekly series, retrieved Oct 9, 2026, 12:03 UTC). Your schedule may use a different series or region, and this is not a freight rate. See weekly diesel by region.
Check one load in five steps
Find the three numbers
Base price (the price at which the surcharge is zero), peg mpg and the index and week it uses. If any is missing from the rate con, ask for the tariff.
Confirm the index week
Many schedules use the last published weekly price before pickup or before delivery. Note which one and the price used.
Compute per mile
(index − base) ÷ peg. Multiply by the eligible miles, loaded only or all.
Compute your real fuel move
Total miles ÷ your actual mpg = gallons. Multiply by the change in price since the base.
Compare and file the gap
Write the difference on the load. Over a month it shows whether your rate or your schedule needs to change.
Schedule types you will see
| Type | How it pays | Watch for |
|---|---|---|
| Per-mile on loaded miles | Formula above × loaded miles | Empty miles earn nothing |
| Per-mile on all miles | Formula × loaded + empty | Check how "all miles" is defined |
| Percent of linehaul | Percent set by an index band | Percent of a low rate can be small |
| Flat per load | A fixed amount per load | Does not move with the index |
| Rolled into the rate | No separate line | You carry the fuel move; price it into the rate |
Structures are general descriptions of common practice, not from a fetched source. Your tariff governs.
Worked example EXAMPLE VALUES
Invented numbers. Base $3.60, peg 6.0 mpg, index this week $4.00. A load runs 500 loaded miles plus 100 empty miles. The truck actually gets 6.5 mpg.
- Surcharge per mile: ($4.00 − $3.60) ÷ 6.0 = $0.0667.
- Paid on loaded miles only: 500 × $0.0667 = $33.33.
- Gallons used: 600 ÷ 6.5 = 92.3. Extra cost vs base: 92.3 × $0.40 = $36.92.
- Gap: $36.92 − $33.33 = $3.59 not recovered on this load.
Small per load. At scale, with the index higher and more empty miles, the gap grows. Use the diesel sensitivity tool to see it on your numbers.
Fuel surcharge check to copy
Keep a row per load. The gap column is the number to bring to the next rate talk.
What we would check in your audit
- Whether the fuel surcharge line on each invoice equals the formula on the rate con.
- Loads where the surcharge was left off or paid on the wrong miles.
- Lanes where empty miles are high enough to turn a small gap into a big one.
- Brokers that fold the surcharge into the rate and quote a lower base.
Questions
Is the surcharge the same as a fuel cost increase?
No. It is a formula tied to an index. Your real cost depends on where you fuel, your discounts and your mpg.
Should I use my actual mpg?
Use it for your own cost check. The schedule uses its own peg.
Which index is correct?
The one named in the rate con or tariff. We do not tell you which series to use.
Is the EIA number what I pay?
No. It is a weekly retail average for a region, shown for context only.
Related: diesel sensitivity, weekly diesel by region, diesel seasonality, deadhead miles, true RPM, cost per mile, rate con vs invoice mismatch, diesel price shock pilot.
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