How much oil do I mix at 50:1?

Divide the gasoline by 50: one US gallon (128 fl oz) takes 2.56 fl oz of oil, and a 5-gallon can takes 12.8 fl oz. In metric, 5 liters takes 3.38 fl oz (100 ml).

How much oil is 40:1 per gallon?

3.2 fl oz per US gallon — 128 ÷ 40. Per liter it works out to about 0.85 fl oz (25 ml).

What happens if the ratio is wrong?

Running lean on oil overheats the piston and can seize the engine in minutes. Running rich fouls spark plugs, blows smoke, and builds carbon in the exhaust ports — gradual damage either way, which is why the mix should be measured, not guessed.

Can I use regular motor oil in my 2-stroke?

No. Premix needs two-cycle oil rated for the application; standard motor oil is formulated for a sump, does not stay dissolved in gasoline, and leaves deposits in the engine. Certified 2-stroke oil costs little more per gallon of mix.

How long does premixed fuel last?

Plan to use it within about 30 days, since ethanol-blended gasoline attracts water and degrades. Two-stroke mixes with fuel stabilizer can stretch to a season, but a fresh, labeled can is cheaper than a carburetor.

Can I mix directly in the equipment tank?

Small tanks make ratios error-prone. Prefer a graduated fuel can: add the measured oil first, then the gasoline so the splash does the stirring, shake, and fill the tool from that stock mix.

Oil to Gas Ratio Calculator | Online Calculators Free

Why premix ratios matter

Two-stroke engines — chainsaws, string trimmers, leaf blowers, older outboards — have no oil sump. Their lubrication rides in the fuel, so every can of gas must carry the exact ratio of two-cycle oil the manufacturer specified. Too little oil scorches the cylinder; too much fouls plugs and cakes ports with carbon.

The arithmetic

A ratio of gas to oil means oil = gasoline ÷ ratio, both in the same volume units. A US gallon is 128 fl oz, so 50:1 takes 2.56 fl oz per gallon, 40:1 takes 3.2, and 32:1 takes 4.0. The board converts to milliliters (1 fl oz = 29.5735 ml) and tablespoons (1 tbsp = 0.5 fl oz) for measuring-cup accuracy.

Which ratio does my tool need?

Modern hand-held equipment almost universally runs 50:1. Many mid-size machines specify 40:1, and legacy chainsaws and outboards often call for 32:1. The decal on the fuel cap or the owner’s manual is the final word — when a tool lists a break-in ratio, use the richer mix for the stated hours, then switch.

Worked example

A chainsaw specifies 50:1 and you are filling a 1-gallon can.
Gasoline: 1 gal × 128 = 128 fl oz.
Oil: 128 ÷ 50 = 2.56 fl oz (75.7 ml, about 5 tablespoons).
For a 5-gallon can, quintuple it: 12.8 fl oz of oil.

How to use it

Find the ratio on the fuel-cap decal or in the manual, then pick it here.
Enter how much gasoline you are mixing and its unit.
Read the oil in fluid ounces, milliliters, or tablespoons.
Add oil to the can, then gas, seal, and slosh to mix — label the can.