A Spirit Level or Bubble Level is an instrument which was design to indicate the angle of any horizontal or vertical surface. Spirit level is handy, accurate and easy to use.

Where to use??
A spirit level is usually used in construction, carpentry and photography to determine if object on which you are working is perfectly level or not. This help you hanging a painting on wall.

How much accurate??
It is almost 100% accurate. Your device should already be calibrated by the manufacturer. In case you believe it is wrongly calibrated you can recalibrate your device by clicking calibration option, placing your device screen facing up on a perfectly leveled surface (like the floor of your room) and press SET. Press RESET to return your device to default factory calibration.