MQ-5 sensor into PPM values

I'm using MQ-5 gas sensor. Do you know how I can get ppm values? Thank you

To get PPM values, it is absolutely necessary to calibrate the sensor against one or more known, accurate standards.

Don't expect the calibration to be stable for long periods of time, or to be very accurate.

Can you teach me how to calibrate?

Google "calibrate sensor" for background material. Here is one introduction: Why Calibrate? | Calibrating Sensors | Adafruit Learning System

Thank you very much!

Is there any formula in conversion of Analog output to PPM?

Is there any formula in conversion of Analog output to PPM?

Calibration gives you the formula.

Hi, depending on your intended use, ie not for life safety as the sole detection device in any such application, you can simply map the sensor across the sensing range given on the datasheet.

Before anyone jumps all over me, yes JRemington is absolutely correct that it must be calibrated to a known concentration of target gas in order to be considered accurate. But I am going to assume you don't have access to cylinders of LPG or natural gas in known precise concentrations to do this.

But you can...again...DON'T TRUST YOUR LIFE OR PROPERTY TO THIS!...you can install the recommended resistor according to the datasheet (10k - 47k) and then run it at 5 volts in your Arduino for a day, then see where the ADC is at (probably around 400-450). Then map that number as:
map(value, 0, 1023, 0, 10000);