# Gas Oil Ratio Calculator (2-Stroke Mix)

URL: https://speedycalculator.com/calculators/everyday-life/gas-oil-ratio/
Last updated: 2026-10-25

> The gas oil ratio calculator works out how much two-stroke oil to add to petrol for 50:1, 40:1, 32:1, 25:1 or any custom mix, in fluid ounces and millilitres.

## Inputs

- Mix ratio (gas : oil)
- Custom ratio
- Gas (petrol) volume (US gal, L, UK gal)

## Results

- Oil to add
- Total mixture

## Formula

```
Oil = gas volume ÷ ratio
Total mix = gas + oil
```

## Explanation

Two-stroke engines in chainsaws, trimmers, outboards and dirt bikes are lubricated by oil mixed into the fuel. Too little oil scores the cylinder; too much fouls plugs and smokes. Always use the ratio in the owner's manual – most modern equipment uses 50:1, older engines 32:1 or 25:1.

### How to use the Gas Oil Ratio Calculator

- **Mix ratio (gas : oil)**
- **Custom ratio**
- **Gas (petrol) volume**
- Every result field is editable: type into **Oil to add** and **Gas (petrol) volume** plus every other field update to match.

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

### How it works

Choose the ratio (or enter your own) and the amount of gas. Type an oil amount into the result to find how much gas it mixes with.

### Oil per amount of gas

Gas25:132:140:150:11 US gal5.1 fl oz4.0 fl oz3.2 fl oz2.6 fl oz2.5 US gal12.8 fl oz10.0 fl oz8.0 fl oz6.4 fl oz5 US gal25.6 fl oz20.0 fl oz16.0 fl oz12.8 fl oz1 L40 mL31 mL25 mL20 mL5 L200 mL156 mL125 mL100 mL

### 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 enterMix ratio (gas : oil)Choose one: 50 : 1, 40 : 1, 32 : 1, 25 : 1 …Custom ratioA numberGas (petrol) volumeUnits: US gal, L, UK gal

## Worked example

Inputs — Mix ratio (gas : oil): 50 : 1; Custom ratio: 60; Gas (petrol) volume: 1 US gal.

Results — **Oil to add = 2.56 fl oz**; Total mixture = 1.02 US gal.

## FAQ

**How much oil for 1 gallon at 50:1?**
2.6 fl oz (76 mL).

**How much oil per litre at 40:1?**
25 mL.

**Can I store mixed fuel?**
Use it within about 30 days, or add a fuel stabiliser; ethanol blends absorb water over time.

**What formula does the Gas Oil Ratio Calculator use?**
Oil = gas volume ÷ ratio.