DEF Consumption Calculator

Diesel exhaust fluid (DEF, sold as AdBlue in Europe) is sprayed into the exhaust of trucks with selective catalytic reduction (SCR) to cut nitrogen oxide emissions. The engine doses it in proportion to the fuel it burns, so DEF use can be estimated from distance, fuel economy and the dosing rate. This calculator gives the volume, the cost and how far one tank of DEF lasts.

How to use this tool

1. Choose US units or metric units.
2. Enter the distance for the period you want to budget, and your fuel economy.
3. Enter the dosing rate as a percentage of diesel used.
4. Add the DEF price and tank size to see the cost and range per tank.

Formula

Diesel used = distance ÷ mpg (or distance × L/100 km ÷ 100)

DEF used = diesel used × dosing rate ÷ 100; range per tank = tank size ÷ DEF used per mile

The dosing rate is the ratio of DEF to diesel by volume. Because the result scales with fuel burned, anything that raises fuel use, such as heavier loads or hilly routes, raises DEF use too. The selected ratio is an estimate, not an engine-control rule; use your manufacturer guidance and fill records. Gallons here are US gallons. A tank size of zero skips range estimates.

Example

A truck drives 1,000 miles at 5 mpg, burning 200 gallons of diesel. At a 2% dosing rate it uses 200 × 0.02 = 4 gallons of DEF, which costs $12 at $3.00 a gallon. A 10-gallon DEF tank would last 10 ÷ 0.004 = 2,500 miles.