Snell's Law Calculator
Calculate the refraction angle of light passing between two media from their refractive indices and the incidence angle, using Snell's law.
Formula: n₁ × sin(θ₁) = n₂ × sin(θ₂)
About Snell's Law Calculator
Snell's Law Calculator is a free online calculator that gives you an instant, accurate result as you type. Calculate the refraction angle of light passing between two media from their refractive indices and the incidence angle, using Snell's law.
The calculation uses the standard formula n₁ × sin(θ₁) = n₂ × sin(θ₂) and updates live with every change to the inputs. Everything runs client-side in your browser — fast, private, and free to use as often as you like.
Common refractive indices: vacuum 1.0, water 1.33, window glass about 1.52, and diamond 2.42 — the source of its brilliant sparkle.
Frequently Asked Questions
Is Snell's Law Calculator free to use?
Yes. Snell's Law Calculator is completely free, with no sign-up, no downloads, and no usage limits. You can use it as many times as you like on any device with a web browser.
How accurate is this calculator?
The calculator applies the standard formula (n₁ × sin(θ₁) = n₂ × sin(θ₂)) with full floating-point precision and rounds only the displayed result. For most practical purposes the results are exact.
Why does the result show 90° sometimes?
If n₁·sin(θ₁)/n₂ exceeds 1, the light undergoes total internal reflection and no refracted ray exists; the tool caps the angle at 90°.
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