Mirror Equation Calculator
Solve the mirror equation (1/f = 1/do + 1/di) for any unknown: focal length, object distance, or image distance.
Use the Mirror Equation Calculator
Mirror Equation Solver
1/f = 1/d₀ + 1/dᵢ | m = −dᵢ / d₀
Positive = concave | Negative = convex
Usually positive (object in front of mirror)
Positive = real (front) | Negative = virtual (behind)
Enter two known values and click Calculate.
Result
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cm
Focal Length
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Object Distance
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Image Distance
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Magnification
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Image Properties
Type
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Orientation
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Size
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Ray Diagram
Summary
The mirror equation (1/f = 1/do + 1/di) relates the focal length of a curved mirror to the object and image distances. This calculator solves for any one of the three variables when the other two are known, and also computes the magnification and characterizes the resulting image.
How it works
- Select which variable you want to solve for: focal length, object distance, or image distance.
- Enter the known values in the input fields using the sign convention (positive = real/in front; negative = virtual/behind).
- Click Calculate to apply the mirror equation and see the result.
- Review the magnification, image orientation, and image type (real vs. virtual) shown below the result.
- Enter a positive focal length for a concave mirror or a negative focal length for a convex mirror.
Use cases
- Solve optics homework problems involving curved mirrors.
- Verify lab results for concave or convex mirror experiments.
- Determine where an image forms for a given object placement.
- Calculate the focal length needed to produce a specific image distance.
- Understand image properties (real/virtual, upright/inverted, magnified/diminished).
- Prepare for physics exams covering geometric optics.
Frequently Asked Questions
Last updated: 2026-05-23 · Reviewed by Nham Vu