Prism Diopter Calculator

Calculate prism diopters from measured displacement and distance. Uses the standard prism diopter definition and Prentice's rule.

Displacement

Distance

Tab to move between fields

Prism Diopters (Δ)

1 Δ

Deviation Angle0.57°

Direction (1=Standard)1

How to Use This Calculator

Measure the Displacement — how far the image or light is shifted in centimeters at the measurement plane.
Enter the Distance from the prism or lens to the measurement plane in centimeters (100 cm = 1 meter is standard).
The calculator applies the prism diopter formula: Δ = displacement × 100 / distance.
Review the Prism Diopters (Δ) result and Deviation Angle in degrees.
Use the result to specify prism prescription, evaluate strabismus deviation, or verify Prentice's rule for decentered lenses.

How the result changes with Displacement

Displacement: Measured displacement or decentration in centimeters.
Distance: Distance from the prism or lens to the measurement plane in centimeters (typically 100 cm = 1 meter).

Prism Diopters (Δ) = displacement(cm) × 100 / distance(cm)

Identify Input Parameters
Displacement = 1, Distance = 100 = 2 input(s) provided
Calculate Prism Diopters
Prism Diopters
1 = 1
Calculate Deviation Angle
Deviation Angle
0.57 = 0.57
Calculate Direction
Direction
1 = 1

Engine last updated August 5, 2026. Checked against 3 independently-derived tests — how we verify calculators.

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