This calculator will determine the Standard Deviation from a know set of measurements.

The mathematical
formula used calculates one standard deviation, which represents approximately
32 per cent of the points that will fall within the normal curve, as shown in Fig. a. One standard
deviation is also called one sigma, or 1σ. Plus or minus one sigma (±1σ) represents 64
per cent of all the points under the normal curve. A wider range on the curve, ±2σ, means
that 95.44 per cent of the points are within the normal curve, and ±3σ means that 99.74 per
cent of the points are within the normal curve. If an infinite number of runs were made,
almost all the measurements would fall within the ±3σ range.

Figure a
Percentages of Points Falling in the ±1σ (64%), ±2σ (95.44%), and ±3σ (99.74%) Ranges