Enter the droplet width and the length of the stain into the calculator to determine the angle of impact. This calculator can also determine the droplet width or splatter length if the other variables are known.

Angle of Impact Formula

The following formula is used to calculate the angle of impact of a blood spatter.

AoI = arcsine (W/L) 
  • Where AoL is the angle of impact (degrees)
  • W is the width of the blood droplet
  • L is the length of the blood splatter

To calculate the angle of impact, take the arcsine value of the width of the droplet and divide it by the length of the splatter.

What is angle of impact?

An angle of impact is a term most often used in forensics to describe the angle at which a droplet of blood has struck a surface.

While the most common use is in forensics, an angle of impact can be used to describe an object that has motion that strikes a surface.

How to calculate angle of impact?

The following example problem outlines how to calculate an angle of impact of a droplet of blood.

First, determine the width of the droplet. This can be measured through the splatter and should be the shorter of the two measurements. In this case, the droplet is measured to be 1.5 cm in width.

Next, determine the length of the splatter. The longer of the two measurements, this is measured to be 3 cm in this example.

Finally, calculate the angle of impact using the formula above.

AoI = arcsine (W/L)

AoI = arcsine (3/1.5)

AoI = 30 degrees