What the ratio means
A 50:1 mix is 50 parts of fuel to 1 part of oil. To find the oil, divide the fuel by the ratio, then convert to a unit you can measure:
oil = fuel ÷ ratioUS fl oz = US gallons × 128 ÷ ratio ml = liters × 1000 ÷ ratio1 US gallon is 128 US fluid ounces and 1 US fluid ounce is 29.5735 ml, so the calculator can show both whatever unit you enter the fuel in.
Worked examples
- 1 gallon at 50:1: 128 ÷ 50 = 2.56 fl oz, which is 75.7 ml.
- 1 gallon at 32:1: 128 ÷ 32 = 4 fl oz, which is 118.3 ml.
- 2.5 gallons at 50:1: 2.5 × 128 ÷ 50 = 6.4 fl oz (189.3 ml).
- 5 liters at 40:1: 5000 ÷ 40 = 125 ml, which is 4.23 fl oz.
Using the chart
The chart below the calculator lists the oil for common amounts at 25:1, 32:1, 40:1 and 50:1. With US units it shows 1, 2, 2.5 and 5 gallons; switch to metric for 1, 5, 10 and 20 liters. Each cell gives the oil in both fluid ounces and millilitres, so you can use whichever marks your measuring bottle has.
Which ratio to use
Use the ratio in your owner's manual or on the oil bottle. Engine makers set it for the engine, and some oils are made for a specific ratio. If the two differ, follow the engine maker's manual or ask the dealer; do not guess.
Mixing tips
- Measure the oil with a graduated mixing bottle or a measuring cup marked in ounces or millilitres.
- Pour the oil into the can with part of the fuel, shake, then add the rest of the fuel and shake again.
- Mark the can with the ratio so nobody pours a 32:1 mix into an engine set up for 50:1, or the other way round.
Questions
How much oil do I mix with 1 gallon of gas at 50:1?
2.56 US fl oz, which is 75.7 ml. That is 128 fl oz divided by 50.
How much 2 stroke oil for 1 gallon at 32:1?
4 US fl oz (118.3 ml). 128 divided by 32 is exactly 4.
How much oil for 5 liters at 40:1?
125 ml, which is 4.23 US fl oz. 5000 ml divided by 40 is 125 ml.
What does 50:1 mean for two stroke fuel?
50 parts of fuel to 1 part of oil by volume. A 50:1 mix uses less oil than a 32:1 mix: 2.56 fl oz per gallon instead of 4.