2-Stroke Fuel Mix Calculator

Work out exactly how much two-stroke oil to add to your petrol for any mix ratio — 32:1, 40:1, 50:1 or a ratio of your own — in millilitres and US fluid ounces, for dirt bikes, chainsaws, strimmers and outboards.

Inputs

Fuel amount

Fuel unit

Mix ratio (fuel : oil)

Tab to move between fields

Results

Oil to add

75.7 ml

Oil to add (US fl oz)2.56 fl oz

Finished mix volume3,861.1 ml

Oil share of mix1.96%

Oil per litre of fuel20 ml

Oil per US gallon of fuel2.56 fl oz

Fuel volume3,785.4 ml

How to Use This Calculator

Enter how much petrol you are mixing and pick the unit.
Choose the mix ratio printed in your engine's manual or on the fuel cap.
Read off the oil quantity in millilitres or US fluid ounces.
Check the finished mix volume before choosing a container — the oil adds to the fuel rather than replacing part of it.

How the result changes with Fuel amount

Fuel amount	Oil to add
50	3,785.4 ml
175	13,248.9 ml
325	24,605.2 ml
450	34,068.7 ml

What each input means

Fuel amount: How much petrol you are mixing.
Fuel unit: Units the fuel is measured in.
Mix ratio (fuel : oil): Use the ratio in your engine's manual or on the fuel cap. Modern engines are usually 50:1; older ones and run-in periods are richer.

What each result means

Oil to add: Two-stroke oil to add to the fuel.
Oil to add (US fl oz): Same quantity in US fluid ounces.
Finished mix volume: Fuel plus oil. Size your container to this, not to the fuel alone.
Oil share of mix: Oil as a percentage of the finished mix.
Oil per litre of fuel: Dose rate, so the answer transfers to any container size.
Oil per US gallon of fuel: Dose rate per US gallon.

How this is calculated

Formula

oil = fuel ÷ ratio; finished mix = fuel + oil

Worked example, using the default values

Convert the fuel volume to millilitres
fuel (ml) = amount × ml per unit
1 US gallons × 3785.411784 ml = 3,785.4 ml
Divide by the mix ratio to get the oil volume
oil = fuel ÷ ratio
3,785.4 ml ÷ 50 = 75.7 ml (2.56 US fl oz)
Add the oil to the fuel for the finished mix
total = fuel + oil
3,785.4 ml + 75.7 ml = 3,861.1 ml
Express the oil as a share of the finished mix
oil % = oil ÷ (fuel + oil) × 100
75.7 ÷ 3,861.1 × 100 = 1.961% — 1 part in 51