In this Air-Fuel Ratio (AFR) calculator, we will show you how to find the AFR in just a few seconds.
We will also help you understand what AFR means, the AFR formula, and why it is important for engines.
What is AFR? How does it affect engine efficiency? How to calculate the air-fuel ratio for gasoline or other fuels? Find all the answers here!
This tool is perfect for students, car enthusiasts, and anyone curious about engine performance. Using it will make understanding AFR simple and quick.
⚙️ Air-Fuel Ratio (AFR) Calculator
Calculate the ratio of air to fuel mass in combustion.
📘 Formula Explanation
AFR = Mass of Air ÷ Mass of Fuel
- Mass of Air → Amount of air supplied for combustion (kg).
- Mass of Fuel → Amount of fuel supplied (kg).
- Typical Gasoline AFR = ~14.7:1 (stoichiometric).
📌 Solved Problem Example
A combustion engine requires air and fuel in a specific proportion for efficient burning. Calculate the Air-Fuel Ratio (AFR) when the mass of air supplied is 14.7 kg and the mass of fuel supplied is 1.0 kg.
📝 Step-by-Step Solution
- Step 1: Given Data
Mass of Air = 14.7 kg
Mass of Fuel = 1.0 kg - Step 2: Formula
AFR = Mass of Air ÷ Mass of Fuel - Step 3: Substitution
AFR = 14.7 ÷ 1.0 - Step 4: Calculation
AFR = 14.7 : 1 - Final Answer:
The Air-Fuel Ratio is 14.7 : 1
📊 AFR Calculation Flow Diagram
📊 Reference Table: Stoichiometric AFR Values
This table provides typical stoichiometric air-fuel ratios for common fuels:
| Fuel Type | Stoichiometric AFR (Air : Fuel) |
|---|---|
| Gasoline (Petrol) | 14.7 : 1 |
| Diesel | 14.5 : 1 |
| Ethanol | 9.0 : 1 |
| Methanol | 6.4 : 1 |
| Propane (LPG) | 15.7 : 1 |
| Natural Gas (CNG) | 17.2 : 1 |
| Hydrogen | 34.3 : 1 |
| Butane | 15.4 : 1 |
| Acetylene | 13.2 : 1 |
| Hexane | 15.1 : 1 |
| Toluene | 13.5 : 1 |
FAQs
What is the AFR and how should you use it?
The air-fuel ratio is how much air you feed into a given quantity of fuel. AFR is as important for efficiency, power and emissions in combustion engines. If there’s too much fuel, the mix is “rich”; if there’s too much air, it’s “lean.”
What is stoichiometric ratio in air fuel mixture for gasoline?
For petrol engines, the stoichiometric AFR is approximately 14.7:1.This ratio is considered the perfect balance for complete combustion in most petrol engines.
Can the AFR change with different fuels?
Yes, the stoichiometric ratio depends on the type of fuel. Ethanol burns at about 9:1, methanol at 6.4:1, propane at 15.7:1, and natural gas at 17.2:1. Each fuel has its own “ideal” AFR for complete combustion.