Fuel Surcharge Calculator
DOE index and mpg to per-mile and trip surcharge.
What it does
Diesel swings make flat freight rates a gamble, so contracts split fuel out as a surcharge. The DOE index sets the price, the peg sets the floor, and mpg converts gallons into miles. Three inputs price any run.
The tool above divides index-minus-peg by mpg for the per-mile figure, multiplies by miles, and shows gallons burned as a check. Pull the weekly EIA diesel average first; everything keys off it.
EIA publishes the on-highway diesel series every Monday with a fuel-surcharge explainer, and trucking associations teach the same spread-over-mpg method in contract guides. Banded tables round the smooth math for invoices, but the arithmetic underneath matches.
Bill what the contract says: some step by bands, some lag a week, some floor at zero. When the index sits under the peg, the page correctly reads no surcharge instead of a rebate.
How to use
- Enter the current DOE diesel index.
- Enter the contract peg price.
- Enter truck mpg average.
- Enter run miles.
- Read per-mile, total, and gallons.
- Bill per the contract table if it steps.
Formula
- index
- DOE weekly diesel average in $/gal.
- peg
- Contract base price in $/gal.
- mpg
- Truck fuel economy.
- miles
- Loaded miles on the run.
Index and peg share dollars per gallon; mpg is the truck average. Negative spreads floor at zero rather than rebating. Gallons burned (miles / mpg) is shown to sanity-check the fuel side.
Worked example
Example: 1000 miles at DOE 3.90
1000 mile run at DOE 3.90 with a 1.25 peg and 6.5 mpg.
- DOE index 3.90, peg 1.25, truck 6.5 mpg.
- Spread: 3.90 - 1.25 = 2.65.
- Per mile: 2.65 / 6.5 = 0.408 $/mi.
- Run is 1000 miles: 0.408 x 1000 = $407.69.
- Fuel burned: 1000 / 6.5 = 153.8 gal.
Reference table
| DOE index | Spread | Per mile |
|---|---|---|
| 3.00 | 1.75 | 0.269 $/mi |
| 3.50 | 2.25 | 0.346 $/mi |
| 4.00 | 2.75 | 0.423 $/mi |
| 4.50 | 3.25 | 0.500 $/mi |
| 5.00 | 3.75 | 0.577 $/mi |
Limits
- Contract tables and lags override smooth math.
- Fleet mpg assumed constant across terrain.
- Deadhead treatment follows the contract.
- Index input must be current to bill right.
Common mistakes
- Billing stale index weeks.
- Using brochure mpg instead of fleet average.
- Forgetting deadhead miles.
- Applying surcharge below the peg.
- Mixing gas and diesel indexes.
Try it yourself
Quick checks. Answers sit tucked under each question.
Surcharge for 500 miles at 4.10, peg 1.20, 6 mpg?
Spread is 4.10 - 1.20 = 2.90. Per mile is 2.90 / 6.0 = 0.483 $/mi. Total is $241.67 on 83.3 gal.
Surcharge for 800 miles at 3.50, peg 1.25, 7 mpg?
Spread is 3.50 - 1.25 = 2.25. Per mile is 2.25 / 7.0 = 0.321 $/mi. Total on 800 miles is $257.14.
Questions
Which index do contracts use?
The DOE weekly on-highway diesel average, published Mondays by EIA. Contracts name it so neither side argues the pump price. This page takes your typed index, so pull the current figure first.
What is the peg price?
The fuel price where surcharge starts, often near 1.20 to 1.25 from older contracts. Spread above the peg divides by mpg. Below the peg the surcharge reads zero.
Whose mpg applies?
Fuel economy of the truck, often near 6 to 7 mpg loaded. Better mpg trims the per-mile figure at the same index. Use fleet average, not brochure best.
Do contracts use tables instead?
Yes, and most do: tables step the surcharge by index bands instead of smooth math. This page computes the smooth value; round to the contract table when billing.
What about empty miles?
Empty miles burn fuel too. Either fold them into the loaded rate or bill them separately per the contract. Unpaid deadhead sinks the surcharge math.
How often does the surcharge reset?
Weekly, when EIA posts the update. Lags and floors vary by contract, so read whether yours resets Monday or trails a week.