What this Fuel Mix Calculator does

This calculator gives the exact amount of 2-stroke oil you must add to gasoline to reach any fuel-to-oil premix ratio (for example 50:1, 40:1, 25:1 or a custom ratio).

It supports common units (US gallons, Imperial gallons, liters, milliliters, fluid ounces) and works either “mix by fuel” (enter a fuel volume → get oil) or “mix by oil” (enter oil volume → get fuel). It’s meant for hobbyists, mechanics and marine/ powersports users who want accurate premix volumes.

How to use

1. Choose the mode: “Mix by Fuel Amount” (default) or “Mix by Oil Amount”.
2. Enter the fuel volume (e.g., 1 US gallon or 5 liters) or enter the oil amount if you’re starting from oil.
3. Pick the fuel / oil unit from the dropdown.
4. Choose a preset ratio (50:1, 40:1, 25:1, 100:1 etc.) or type a custom ratio into the ratio box.
5. Read the primary result and the unit conversions (ml, fl-oz, tablespoons).

The simple math behind the calculator

Everything here uses two base conversion facts:

• 1 US gallon = 128.00 fluid ounces (fl oz)
• 1 fluid ounce ≈ 29.5735 milliliters (ml)

UK/Imperial gallons, the calculator uses 1 Imperial gallon = 160 fl oz that’s why results change if you switch fuel unit.

Core formulas

• Convert fuel to fluid ounces (for US gallons / liters):
  fuel_fl_oz = fuel_volume * oz_per_unit
  where oz_per_unit is 128 for US gallons, 160 for UK gallons, 33.814 for liters (fl oz per liter).
• Oil volume (in fl oz) for a ratio R (written as R:1) =
  oil_fl_oz = fuel_fl_oz / R
• Convert oil fl-oz to milliliters:
  oil_ml = oil_fl_oz × 29.5735
• If you start with oil and need fuel:
  fuel_fl_oz = oil_fl_oz × R → convert back to gallons or liters.

Example (50:1, 1 US gallon):
fuel_fl_oz = 1 × 128 = 128 fl oz → oil_fl_oz = 128 / 50 = 2.56 fl oz → oil_ml = 2.56 × 29.5735 ≈ 75.7 ml.

Quick reference tables (common ratios)

US gallons → oil (fluid ounces) and ml

Ratio	Fuel (US gal)	Oil (fl oz)	Oil (ml)
100:1	0.5 gal	0.64 fl oz	18.9 ml
	1 gal	1.28 fl oz	37.9 ml
	1.5 gal	1.92 fl oz	56.8 ml
	2 gal	2.56 fl oz	75.7 ml
	2.5 gal	3.20 fl oz	94.6 ml
	3 gal	3.84 fl oz	113.6 ml
	4 gal	5.12 fl oz	151.4 ml
	5 gal	6.40 fl oz	189.3 ml
	7.5 gal	9.60 fl oz	283.9 ml
	10 gal	12.8 fl oz	378.5 ml
50:1	0.5 gal	1.28 fl oz	37.9 ml
	1 gal	2.56 fl oz	75.7 ml
	1.5 gal	3.84 fl oz	113.6 ml
	2 gal	5.12 fl oz	151.4 ml
	2.5 gal	6.40 fl oz	189.3 ml
	3 gal	7.68 fl oz	227.1 ml
	4 gal	10.2 fl oz	302.8 ml
	5 gal	12.8 fl oz	378.5 ml
40:1	0.5 gal	1.60 fl oz	47.4 ml
	1 gal	3.20 fl oz	94.6 ml
	1.5 gal	4.80 fl oz	142.0 ml
	2 gal	6.40 fl oz	189.3 ml
	2.5 gal	8.00 fl oz	236.9 ml
	3 gal	9.60 fl oz	283.9 ml
	4 gal	12.8 fl oz	378.5 ml
	5 gal	16.0 fl oz	473.2 ml
25:1	0.5 gal	2.56 fl oz	75.7 ml
	1 gal	5.12 fl oz	151.4 ml
	1.5 gal	7.68 fl oz	227.1 ml
	2 gal	10.2 fl oz	302.8 ml
	2.5 gal	12.8 fl oz	378.5 ml
	3 gal	15.4 fl oz	454.2 ml
	4 gal	20.5 fl oz	606.0 ml
	5 gal	25.6 fl oz	757.1 ml

Liters → oil (milliliters and fl-oz)

Ratio	Fuel (L)	Oil (ml)	Oil (fl oz)
100:1	0.5 L	18.9 ml	0.64 fl oz
	1 L	37.9 ml	1.28 fl oz
	1.5 L	56.8 ml	1.92 fl oz
	2 L	75.7 ml	2.56 fl oz
	2.5 L	94.6 ml	3.20 fl oz
	3 L	113.6 ml	3.84 fl oz
	4 L	151.4 ml	5.12 fl oz
	5 L	189.3 ml	6.40 fl oz
50:1	0.5 L	37.9 ml	1.28 fl oz
	1 L	75.7 ml	2.56 fl oz
	1.5 L	113.6 ml	3.84 fl oz
	2 L	151.4 ml	5.12 fl oz
	2.5 L	189.3 ml	6.40 fl oz
	3 L	227.1 ml	7.68 fl oz
40:1	1 L	94.6 ml	3.20 fl oz
25:1	1 L	151.4 ml	5.12 fl oz

Practical rules and tips

• Always follow equipment makers’ recommended ratio first modern high-performance synthetic oils sometimes recommend leaner mixtures (e.g., 100:1 for some injector oils); when in doubt use a slightly richer mix rather than leaner.
• Measure with graduated containers or syringe-type oil dispensers for small amounts tablespoons and visual guesstimates lead to errors.
• Mix oil into fuel, then shake the container for a uniform premix. Do not add fuel to oil. (Mixing instruction text in your tool reflects this.)
• For marine/outboard engines, seasonal storage with a slightly richer mix helps protect inlet ports; check the manufacturer.

What each parameter means

• Mode (Mix by Fuel / Mix by Oil): Which quantity you start with fuel volume to get oil needed, or oil amount to find how much fuel it will mix with.
• Fuel Amount: The volume of gasoline you plan to premix (enter numeric value only).
• Fuel Unit: Unit that fuel amount is measured in (US gal, UK gal, L, ml, fl oz). Unit changes conversions.
• Oil Amount: When in oil mode, the volume of oil you have/are adding.
• Oil Unit: Unit for oil (ml, cc, fl oz). A cc equals 1 ml.
• Ratio (R:1): The parts of fuel per one part of oil (e.g., 50:1 means 50 parts fuel to 1 part oil).
• Preset Ratios: Convenient common values (16:1 → very rich, 50:1 → common for many two-stroke oils, 100:1 → used with modern special injector oils).