Two-Stroke Fuel Mix Calculator
Calculate the right petrol to oil ratio for two-stroke engines like 50:1 or 40:1 from your fuel tank size, free in your browser.
Enter Values
Minimum 1
How to use this calculator
- Enter the litres of petrol and the mix ratio (the oil part of petrol:oil).
- Read the millilitres of oil to add.
How it works
Oil (mL) = petrol (L) × 1000 ÷ ratio. A 50:1 mix of 5 L needs 5000 ÷ 50 = 100 mL of oil.
Worked example
5 L petrol at 50:1. Add 100 mL of two-stroke oil.
Common mistakes
- Guessing the ratio — always use the ratio specified for your engine.
- Mixing too much oil, which fouls plugs and smokes; too little risks seizing.
Frequently asked questions
How do I mix two-stroke fuel?
Mix petrol and oil to the ratio your engine specifies — 50:1 means 100 mL of oil per 5 L of petrol. The tool works out the oil for any fuel amount.
What happens if the ratio is wrong?
Too little oil starves the engine of lubrication and can seize it; too much fouls the plug and smokes. Always use the manufacturer's ratio.
What ratio should I use?
Follow your engine's manual — common ratios are 50:1, 40:1 and 25:1. When unsure, check the cap or handbook.
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Cite this tool
Zerdly. (2026). Two-Stroke Fuel Mix Calculator. Retrieved from https://www.zerdly.com/tools/two-stroke-fuel-mix-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.