Fuel Calculator
Advanced Pit Strategy
Drag each stint to set how much fuel you load — the estimated laps update accordingly.
How to use the fuel calculator
This tool works out exactly how much fuel to load for an iRacing race, how many pit stops you'll need and how long each stint lasts. You only need three numbers: your race length, your race-pace lap time and how much fuel your car burns per lap.
- Choose your race format. Pick Time-based for a timed race (RPM GT3 races are 90 minutes) or Lap-based if the race is a fixed number of laps.
- Enter the race length. Set the duration in hours and minutes, or the number of laps.
- Enter your lap time. Use a realistic race-pace lap (including traffic), not your best qualifying lap — a faster time means more laps and more fuel.
- Enter fuel per lap. In iRacing, run at least 5 laps at race pace and read your usage from the black box (press F4, or check the fuel page): the "fuel used last lap" / average figure is what you enter here.
- Set the tank size. Enter your car's usable tank in litres. In RPM races the tank is limited to 65%, so enter 65% of the car's full capacity.
- Add a safety margin. One or two extra laps covers the formation lap, a safety car or a slightly thirstier run — it's always better to finish with a splash to spare.
- Read the results & plan your stops. You get total laps, total fuel needed, estimated pit stops and laps per stint. Drag the stints in Advanced Pit Strategy to fine-tune how much fuel to load at each stop.
Tips for accurate fuel numbers
- Always measure consumption at race pace with a full tank — fuel use rises with a heavier car and drops when you lift-and-coast.
- Fuel is weight: roughly 0.72 kg per litre. Carrying 20 litres you don't need costs lap time, so fill for the race plus a sensible margin, not for comfort.
- Consumption changes with your setup and driving aids, so re-check it after any big setup change or a switch of car/track.
FAQ
How do I find my fuel per lap in iRacing?
Do a short run at race pace, then open the black box with F4 (or the fuel page). It shows the fuel used on the last lap and a rolling average — use that average, ideally over 5+ clean laps.
How much safety margin should I add?
One extra lap is a good default; add two if there's a full formation lap or a likely safety car. Timed races also often run an extra lap past the clock, which the margin covers.
Does it work for endurance races?
Yes. Enter the full race duration (or lap count) and the calculator splits it into stints with pit stops; the stint planner lets you set the fuel load per stop.