Mix 2-stroke fuel with confidence. This free 2 stroke fuel ratio calculator and 2 stroke oil gas mix calculator converts any fuel amount to the exact oil dose for 50:1, 40:1, 33:1, 32:1, 25:1 or a custom ratio — with one-click presets for Stihl, Husqvarna, Echo and vintage equipment, a reverse oil-to-fuel solver, a batch fuel mix calculator for multiple cans, and a cost-per-tank estimator.
Important: always follow the manufacturer ratio printed in your equipment manual. Running the wrong mix can seize a 2-stroke engine.
Already poured the oil? Find out how much petrol it treats.
Mixing several cans at once? Enter each can and get the oil dose per can plus the batch total.
These presets come straight from the manufacturers' own manuals and product pages (see sources below). Pick one above and the calculator fills in the ratio.
| Equipment / oil | Ratio | Oil per litre | Notes |
|---|---|---|---|
| Stihl — 50:1 (STIHL 2-stroke oil) | 50:1 | 20 ml | All modern Stihl 2-stroke handheld equipment. 20 ml oil per litre of petrol. |
| Husqvarna — 50:1 (Husqvarna oil) | 50:1 | 20 ml | Husqvarna oil in Husqvarna saws, trimmers and blowers. 100 ml per 5 litres. |
| Husqvarna — 33:1 (generic JASO FB / ISO EGB oil) | 33:1 | 30.3 ml | Non-Husqvarna air-cooled 2-stroke oil, per the Husqvarna operator manual. |
| Echo — 50:1 (PowerBlend / Red Armor) | 50:1 | 20 ml | All Echo 2-stroke equipment with 89+ octane petrol. 2.6 fl oz per US gallon. |
| Modern outboard — 50:1 | 50:1 | 20 ml | Most modern 2-stroke outboards. Use TCW water-cooled oil here, never in air-cooled saws. |
| Vintage / generic — 40:1 | 40:1 | 25 ml | Common on older saws and trimmers, including pre-1990 Stihl models. Check the manual. |
| Vintage — 32:1 | 32:1 | 31.3 ml | Older trimmers, mopeds and small 2-stroke engines. |
| Vintage — 25:1 | 25:1 | 40 ml | Older European 2-stroke equipment. |
| Vintage — 16:1 | 16:1 | 62.5 ml | Very old engines and some break-in schedules. |
| Honda 4-stroke (GX25/GX35) — no mix | no mix | — (no mix) | Honda mini 4-stroke engines take straight unleaded petrol; oil lives in a separate sump. |
| Custom ratio… | any | — | Enter any ratio from your operator manual. |
Honda is the odd one out: the Honda GX25/GX35 mini 4-stroke engines take straight unleaded petrol — engine oil lives in a separate 0.08 L sump and is never mixed into the fuel.
| Petrol | STIHL oil |
|---|---|
| 1 L | 20 ml |
| 2 L | 40 ml |
| 3 L | 60 ml |
| 5 L | 100 ml |
| 10 L | 200 ml |
| 20 L | 400 ml |
Source: official STIHL dealer mixing guide (stihlshop.co.nz): 20 ml oil per litre of petrol. Minimum 90 RON petrol.
| Petrol | Oil at 50:1 | Oil at 33:1 (exact) |
|---|---|---|
| 5 L | 100 ml | 151.5 ml |
| 10 L | 200 ml | 303 ml |
| 15 L | 300 ml | 454.5 ml |
| 20 L | 400 ml | 606.1 ml |
Source: Husqvarna 372 XP / 555 / 55 Rancher operator manuals. The printed manual rounds the 33:1 column (0.15 / 0.30 / 0.45 / 0.60 L); exact values are shown here.
2.6 fl oz of Echo PowerBlend oil per 1 US gallon of 89+ octane petrol (128 / 50 = 2.56 fl oz, rounded up). Source: echo-usa.com PowerBlend Gold product page.
How is your mix stored?
Enter the amount of petrol you want to mix, pick a ratio preset (Stihl 50:1, Husqvarna 50:1 or 33:1, Echo 50:1) or type a custom ratio, and the calculator divides fuel by ratio: oil = fuel / ratio. For example, 5 litres at 50:1 need 100 ml of oil (3.38 fl oz), and switching the same 5 litres to 40:1 raises it to 125 ml.
A 50:1 fuel mix means 50 parts petrol to 1 part 2-stroke oil, which is 2% oil. In practice: 5 litres of petrol need 100 ml of oil, 1 litre needs 20 ml, and 1 US gallon needs 2.56 fl oz (75.7 ml). Stihl, Husqvarna and Echo all specify 50:1 for their modern 2-stroke handheld equipment when you use their own brand of oil.
The question of how much oil per gallon 50:1 needs comes down to simple division: one US gallon is 128 fluid ounces, so 128 / 50 = 2.56 fl oz of oil per gallon at 50:1. That is why oil makers sell 2.6 oz oil per gallon single-serve bottles: 2.6 fl oz is 2.56 rounded up for easy measuring. For 2 gallons use 5.12 fl oz, and for 5 gallons use 12.8 fl oz. In metric, 1 gallon (3.785 L) needs 75.7 ml of oil.
A 40:1 mix chart converts fuel to oil at 40 parts petrol to 1 part oil: 1 litre gives 25 ml of oil, 2 litres give 50 ml, 5 litres give 125 ml, 10 litres give 250 ml, and 20 litres give 500 ml. In US units: 1 gallon takes 3.2 fl oz, 2 gallons take 6.4 fl oz. Use the ratio chart mode above for a full 50 to 1 fuel mix chart or any other ratio.
For a modern chainsaw the chainsaw fuel mix ratio is 50:1. Stihl specifies a stihl 50:1 mix with STIHL 2-stroke oil (20 ml per litre), Husqvarna specifies 50:1 with Husqvarna oil or a husqvarna 33:1 mix with generic JASO FB or ISO EGB oil (a 33:1 fuel mixture giving 151.5 ml per 5 litres), and Echo specifies 50:1 with PowerBlend oil. This 2 stroke chainsaw fuel mix calculator has all of them as one-click presets. Saws built before 1990 often need 40:1, so always follow the manufacturer ratio printed in your manual.
For 2 stroke mix litres, multiply litres by 1000 and divide by the ratio: oil (ml) = litres x 1000 / ratio. So 5 litres at 50:1 need 100 ml of oil, at 40:1 need 125 ml, and at 25:1 need 200 ml. That also answers how much 2 stroke oil per litre you need: 1 litre at 50:1 takes 20 ml, and at 40:1 it takes 25 ml.
Most modern 2-stroke outboards run a 50:1 outboard fuel mix with TCW-rated water-cooled oil: 6 US gallons (22.7 litres) need 454.2 ml of oil (15.36 fl oz). Much older outboards may specify 24:1 or 32:1, so check the cowl sticker or manual. Never use TCW outboard oil in an air-cooled chainsaw or trimmer: Stihl and Husqvarna manuals explicitly forbid water-cooled oils in air-cooled engines.
The standard weed eater gas oil ratio for modern trimmers is 50:1: Stihl, Husqvarna and Echo trimmers all run 50:1, which is an echo 50:1 fuel ratio of 2.6 fl oz of oil per gallon (20 ml per litre). Older or generic trimmers may call for a 32:1 fuel mix (31.3 ml per litre) or 40:1 (25 ml per litre), so check the manual. Running straight petrol with no oil in a 2-stroke trimmer will seize the engine within minutes.
In the 25:1 vs 50:1 debate the numbers decide: 1 litre at 25:1 takes 40 ml of oil, exactly twice the 20 ml that 50:1 needs. A richer 25:1 fuel mix in an engine designed for 50:1 causes heavy smoke, carbon build-up and a fouled spark plug, while a leaner 50:1 in a 25:1 engine starves it of lubrication and can seize the piston. Use whichever ratio your manufacturer specifies and never guess.
Yes: this premix calculator includes an oil to fuel calculator reverse mode. Enter the oil you have and it multiplies by the ratio: fuel = oil x ratio. Poured 250 ml of oil for a 50:1 mix? You need 12.5 L of petrol. One 2.6 fl oz bottle at 50:1 treats 1.02 gal of petrol.
Untreated 2 stroke fuel has a short 2 stroke fuel shelf life: use it within about 30 days, because Husqvarna manuals warn never to mix more than a one-month supply. A fuel stabilizer for 2 stroke mix extends that to roughly 90 days; oils with a built-in stabilizer (Echo PowerBlend Gold) are rated for 30+ days; and factory premix such as STIHL MotoMix lasts up to 5 years unopened. Store any mix sealed, cool and dark, shake the can before refuelling, and drain the tank if the tool will sit idle.
The cost per tank 2 stroke calculation is simple: oil per tank = tank size / ratio, then multiply by your oil price per litre. Example: a 0.5 litre tank at 50:1 holds 10 ml of oil; with oil at $25 per litre that is $0.25 of oil per tank. Use the cost mode above with your own tank size and oil price.
Fuel Mix Calculator by nrtechstudio.com — free, 100% in-browser, no data leaves your device. Ratios verified against Stihl, Husqvarna, Echo and Honda manufacturer sources (Oct 2026).