Sight adjustment calculator

How the sum works

Clicks are the distance the group has to move, divided by what one click moves it. One minute of angle is 1.047 inches at 100 yards, about 29 mm at 100 metres, and it scales with distance: a quarter-MOA click moves the group about 1.7 mm at 25 yards. A click of 0.1 mrad moves it 10 mm at 100 metres. Shooting Sports USA explains the MOA sum.

Match aperture sights are often finer. Notch assumes about 0.5 mm per click at 25 yards for NSRA cards, which is where this calculator starts. Check your sight's manual for its real value.

Which way to turn

The group moves the way the rear sight moves. To bring a group that sits right back to centre, the rear sight goes left.

Read the arrows on your own sight before turning. Many US sights mark the direction the group will move. European target sights are often marked for where the shots are: you turn towards H when they are high and towards R when they are right. The CMP's coaching notes cover both markings.

Sight or technique?

A sight change fixes an offset that repeats. Notch suggests one only when the group sits more than 3 mm off centre across a whole competition card. One group off to the side is more often technique, and the pages below cover what to check.

After you adjust

1. Re-zero with a 5-shot group at centre
2. If the pattern persists, check your natural point of aim

These are the steps Notch gives with a sight suggestion. Follow your range's safety rules and your coach's advice.