StepsApp uses your phone's built in step counting sensor (accelerometer sensor in case your device is missing the step counting sensor) to determine if the step has been made and then uses your input for steps length to determine what was the distance you covered approximately.

How to set your step length manually:

• Open StepsApp
• Go to “Settings”
• Click on the “Body Measurements”
• Find “step length” section and adjust your own “step length”
  (If left as “automatic”, the scientific coefficient will be used instead)

How to calculate your step length: (calculated with a scientific coefficient)

Women: height (cm) times 0,413 = your step length in cm
Men: height (cm) times 0,415 = your step length in cm