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Parallax Error Calculator

This quick calculator shows the amount of parallax error that may occur using a fixed-parallax scope to sight onto an object placed at a known distance. 'Maximum parallax error' is in the context of the viewer setting up with their eye centered on the ocular lens -- using it as is normally intended. Strictly speaking the maximum possible error is double the number you will get below if you sight to your destination by peeking through it from the edge of your scope... which nobody actually does. For a true theoretical maximum double the returned result values.

 Objective Lens Diameter 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 Pick a number from the drop-down. Values are in millimeters (mm) Fixed Parallax Setting Enter your scope's fixed parallax range value as a simple number, 1-999, without commas or decimal points. Starting Range Enter the starting range value to report, 1-999, without commas or decimal points. Ending Range Enter the ending range value to report, 1-999, without commas or decimal points. Range Chart Increment 5 10 25 50 100 Pick the increment for the range chart results

### Formulae:

1. Parallax error in millimeters (Pmm): ( 0.5 x D x ( Abs ( R - P ) ) / P
where
• D = Objective diameter in millimeters
• R = range to target
• P = fixed parallax setting of scope
2. Parallax error in inches (Pin): Pmm x 0.0393701
3. Parallax error in Minutes of Angle: Pin / 1.047 / ( R / 100 )
4. Parallax error in Milliradians: Pin / 3.6 / ( R / 100 )