# Percent error

1. Oct 21, 2007

### Joza

How does one calculate percent error in measurements?

In attempting to measure a distance of some centimeters with a meter stick, how could I estimate it?

Isn't a meter stick accurate to the millimeter?

2. Oct 21, 2007

### Manchot

Well, if you use the millimeter marks to measure that distance, the maximum error that you could have would be 1 mm.

3. Oct 21, 2007

### MagikRevolver

That's tolerance interval. It's not a percentage. I think, but don't know, but if you measure 20.2 milimeters on your measuring stick, and the most you can be off by is 1 mm than your percent error is that 1mm over 20.2 gives you percent error of.049, or 5%.

4. Oct 21, 2007

### stewartcs

MagikRevolver is correct.

The relative error is simply the absolute error divided by the actual measurement (the value of the thing you are measuring).

Absolute error is the amount of physical error in a measurement. The absolute error in your case is the smallest division of the meter stick, or 1 mm.

Hence, the relative error in this case is 1 mm/x mm where x is your actual measurement.