Use this calculator when your agreement uses a diesel-price difference divided by an MPG factor. It does not replace a carrier tariff, a percentage table or negotiated contract terms.
The formula shown here
Per-mile fuel adjustment = (current diesel price − contract base diesel price) ÷ contract MPG. Total adjustment = per-mile adjustment × billable miles. The calculator shows the signed result and an alternative that floors a negative adjustment at zero; your agreement decides which applies.
Worked example
With a hypothetical $4 current price, a $3 base and a 5 MPG contract factor, the adjustment is $0.20 per billable mile. Over 500 billable miles, that is $100. These example inputs are not an industry standard or today’s fuel price.
Check four terms before using the result
- Which index and region does the contract name?
- Which release date or averaging period governs this invoice?
- Which miles are billable, and what rounding or price bands apply?
- Does a below-base price produce a credit, zero surcharge or another adjustment?
EIA explains that it publishes weekly diesel data but does not calculate or regulate fuel surcharges. There is no universal formula every shipper must accept.
For the cost of fuel you will actually burn, use the separate trip fuel calculator. Find the dated EIA benchmark here.