# Idling Fuel Consumption Calculator

URL: https://speedycalculator.com/calculators/everyday-life/idling-fuel-consumption/
Last updated: 2026-10-25

> The idling fuel consumption calculator estimates how much fuel and money an engine wastes while idling from its engine size and fuel type, per hour and over days or a year, plus the CO₂ emitted.

## Inputs

- Fuel
- Engine size (L, cc, in³)
- Idling per day (min)
- Days
- Fuel price (/US gal, /L, /UK gal)

## Results

- Idle fuel consumption
- Fuel used
- Cost of idling
- CO₂ emitted

## Formula

```
Idle consumption (L/h) ≈ engine size (L) × 0.6 (petrol) or × 0.45 (diesel)
Fuel used = idle rate × idle time; cost = fuel × price
```

## Explanation

An idling engine burns fuel while going nowhere. A typical 2-litre petrol car uses about 1.2 L (0.3 gallons) an hour, and larger engines more. Turning the engine off for stops longer than about 10 seconds saves fuel in a warm modern car – which is why many cars now have stop-start systems.

### How to use the Idling Fuel Consumption Calculator

- **Fuel**
- **Engine size**
- **Idling per day**
- **Days**
- **Fuel price**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Choose petrol or diesel, enter the engine size, the minutes you idle per day and for how many days, and the fuel price.

### Tips

- Use your own measured figures – fuel economy, speed and prices vary a lot with driving style, traffic, load and season.
- Pick the unit in each field's menu (miles or kilometres, mpg or L/100 km); the calculator converts everything for you.
- Fill up to the brim twice and divide the distance by the fuel added to measure real fuel economy.
- For vehicle modifications, treat results as a starting point and confirm with the parts maker or a professional mechanic.

### Common mistakes to avoid

- Mixing US and imperial (UK) gallons – a UK gallon is about 20% bigger.
- Using the advertised fuel economy instead of real-world figures.
- Forgetting tolls, parking and wear and tear when comparing driving with public transport.

### Inputs explained

FieldWhat to enterFuelChoose one: Petrol, DieselEngine sizeUnits: L, cc, in³Idling per dayIn minDaysA numberFuel priceUnits: /US gal, /L, /UK gal

### What each result means

- **Idle fuel consumption** = [Engine size]×[Fuel]×0.001÷3600
- **Fuel used** = [Idle fuel consumption]×[Idling per day]×60×[Days]
- **Cost of idling** = [Fuel used]×[Fuel price]

### Example values

How the main result changes when **Engine size** changes and everything else stays at the example values above:

Engine size (L)Fuel used (US gal)19.91.514.9219.82.524.8329.7439.6

## Worked example

Inputs — Fuel: Petrol; Engine size: 2 L; Idling per day: 15 min; Days: 250; Fuel price: $3.5 /US gal.

Results — Idle fuel consumption = 1.2 L/h; **Fuel used = 19.8 US gal**; Cost of idling = $69.35; CO₂ emitted = 173 kg.

## FAQ

**How much fuel does idling use?**
About 0.5–0.7 L per hour per litre of engine size for petrol engines – roughly 1–1.5 L/h for a typical car.

**Is it better to idle or restart?**
For a warm engine, restarting uses less fuel than idling for more than about 10 seconds.

**Does idling warm up the engine faster?**
No – gentle driving warms it faster and with less wear than idling.

**What formula does the Idling Fuel Consumption Calculator use?**
Idle consumption (L/h) ≈ engine size (L) × 0.6 (petrol) or × 0.45 (diesel).


## Sources

- [U.S. DOE – Idling reduction](https://afdc.energy.gov/conserve/idle_reduction_basics.html)