How much oil goes in a 50:1 mix?

A 50:1 ratio means 50 parts petrol to 1 part oil, so you divide the fuel by 50. One US gallon at 50:1 is 128 ÷ 50 ≈ 2.6 fluid ounces of oil; one litre is 1000 ÷ 50 = 20 millilitres. Type your ratio and your fuel amount and the tool gives you the oil in both ounces and millilitres.

What ratio should I mix at?

Whatever the engine plate or the manual says — it is set by the machine, not by the fuel, so the ratio is a field you fill in rather than a number this tool assumes. Older saws and trimmers often run 32:1 or 40:1; many newer ones are 50:1. When the two disagree, follow the engine.

Does the ratio number mean petrol-to-oil or oil-to-petrol?

Petrol to oil. 50:1 is 50 measures of gas for every 1 of oil — a lot of fuel, a little oil. Enter the larger number (the 50) in the ratio field here. Getting it upside down floods the engine with oil, so read it as "fifty of gas, one of oil".

Can I mix a big batch and keep it?

Mixed two-stroke fuel goes stale — the petrol oxidises and the additives drop out, often within a month or two. Mix what you will burn in a few weeks, shake the can before each fill, and use a fuel stabiliser if it will sit. This tool sizes the batch; it does not judge how old the can is.

2-stroke fuel mix calculator

This splits the fuel you type by the ratio you type — nothing more. The correct ratio is the one stamped on your engine, not a figure this page picks for you. Mix fresh, shake the can, and when in doubt read the manual before you pull the cord.

Enter how much petrol you are mixing and the ratio the engine wants, and the tool returns the volume of two-stroke oil to add — in fluid ounces and millilitres at once — plus the rough total once the oil is in.

Ejemplo resuelto

You are filling a 1-gallon jug at 50:1. A US gallon is 128 fluid ounces, so the oil is 128 ÷ 50 = 2.56 fl oz, which is about 76 mL. Drop to 40:1 and it climbs to 3.2 fl oz (95 mL); the smaller the ratio number, the more oil goes in.

En la obra

A 5 L can at 40:1. 5,000 mL ÷ 40 = 125 mL of oil. At 50:1 it is 100 mL. Pour the oil into the empty can first, then the fuel, and the sloshing on the way to the truck does the mixing. A graduated oil bottle beats guessing by a mile — 25 mL either way on a small can is a 20% change in the ratio.

Topping up a half-full can. Mix for what you are adding, not the can's size. Putting 2.5 gal into a 5 gal can at 50:1 is 2.5 × 128 ÷ 50 = 6.4 fl oz. Dose the whole can and the mix ends up rich; dose nothing because "there's already oil in there" and it ends up lean, and lean is the one that scores a piston. In litres it is the same move: 10 L into a 20 L can at 50:1 is 10,000 ÷ 50 = 200 mL.

Two saws, two ratios. A 32:1 plate and a 50:1 plate do not share a can. 50:1 in the 32:1 engine is a third less oil than it wants. Mix two cans and mark them — the ratio comes off the plate, and this page only divides by it.

Pruebe un ejercicio

Quick referencefor mix

Oil: fuel ÷ ratio number
Per US gallon: 32:1 4.0 fl oz · 40:1 3.2 · 50:1 2.56
Per litre: 32:1 31 mL · 40:1 25 · 50:1 20
Per 5 L can: 32:1 156 mL · 40:1 125 · 50:1 100
Unidades: 1 US gal = 128 fl oz = 3.785 L · 1 fl oz = 29.6 mL · imperial gallon = 160 imp fl oz
Direction: bigger ratio number = less oil — the plate decides

Waste & overagewhat to add, and why

Mix a touch more than the tank holds, not less — a saw that runs dry mid-cut is worse than 100 mL of mix left in the can, and premix only keeps for weeks, so do not build up a stockpile.
If you split a jerry can between two ratios (a 40:1 blower and a 50:1 saw), label the cans; the fix for a wrong ratio is to dump it, so the extra you buy is a second can, not more fuel.

Mistakes to catchbefore you order

Typing the oil-to-petrol number backwards: 50 means fifty parts fuel to one part oil. If the result says litres of oil for a 5 L can, the ratio went in upside down.
Reading a US gallon can as an imperial one — they differ by about 20%, so 2.5 imperial gallons at 50:1 wants a fifth more oil than the US figure.
Adding oil to a can that already has last week's mix in it; the tool assumes the fuel is straight petrol, so either empty the can or only mix the fresh amount you are adding.

La fórmula

oil = fuel volume ÷ ratio

The ratio is simply how many parts of petrol share one part of oil, so dividing the fuel by it gives the oil directly in the same units. Convert once to a common unit (millilitres here) and the ounce and millilitre figures fall straight out of it.

Preguntas

How much oil goes in a 50:1 mix?: A 50:1 ratio means 50 parts petrol to 1 part oil, so you divide the fuel by 50. One US gallon at 50:1 is 128 ÷ 50 ≈ 2.6 fluid ounces of oil; one litre is 1000 ÷ 50 = 20 millilitres. Type your ratio and your fuel amount and the tool gives you the oil in both ounces and millilitres.
What ratio should I mix at?: Whatever the engine plate or the manual says — it is set by the machine, not by the fuel, so the ratio is a field you fill in rather than a number this tool assumes. Older saws and trimmers often run 32:1 or 40:1; many newer ones are 50:1. When the two disagree, follow the engine.
Does the ratio number mean petrol-to-oil or oil-to-petrol?: Petrol to oil. 50:1 is 50 measures of gas for every 1 of oil — a lot of fuel, a little oil. Enter the larger number (the 50) in the ratio field here. Getting it upside down floods the engine with oil, so read it as "fifty of gas, one of oil".
Can I mix a big batch and keep it?: Mixed two-stroke fuel goes stale — the petrol oxidises and the additives drop out, often within a month or two. Mix what you will burn in a few weeks, shake the can before each fill, and use a fuel stabiliser if it will sit. This tool sizes the batch; it does not judge how old the can is.

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