Mirror Equation Calculator
Enter a focal length or radius of curvature plus one distance, or two distances, to solve the mirror equation 1/f = 1/do + 1/di with the magnification and image type.
How to use the mirror equation calculator
- Enter the focal length or the radius of curvature (f = R/2), then one distance.
- Or leave focal length blank and enter both the object and image distances.
- Read the solved values, the magnification and whether the image is real or virtual.
Examples
Concave mirror, distant object
f = 10 cm (R = 20 cm), object distance do = 30 cm
image distance di = 15 cm, magnification = -0.5 (real, inverted)
From radius of curvature
R = 20 cm, object distance do = 30 cm
focal length f = 10 cm, image distance di = 15 cm
Frequently asked questions
What is the mirror equation?
For a spherical mirror, 1/f = 1/do + 1/di, where f is the focal length, do the object distance and di the image distance.
How are focal length and radius of curvature related?
The focal length is half the radius of curvature, f = R/2. You can enter either one and the calculator finds the other.
What sign convention does this use?
Real is positive. A concave (converging) mirror has a positive focal length and radius; a convex (diverging) mirror has negative values. A real image in front of the mirror has a positive image distance.
How is magnification calculated?
Magnification m = -di / do. Negative means the image is inverted, positive means upright, and the absolute value is the size ratio.
What inputs do I need?
Provide a focal length or radius plus one distance, or provide both distances. Distances of zero are not allowed.
Related tools
Thin Lens Calculator
Solve the thin lens equation 1/f = 1/do + 1/di. Enter any two of focal length, object distance and image distance to find the third, plus magnification.
Lens Maker's Equation Calculator
Find a lens focal length and power from its refractive index and surface radii using 1/f = (n-1)(1/R1 - 1/R2). Supports flat surfaces. Free and instant.
Snell's Law Calculator
Calculate the angle of refraction with Snell's law, n1 sin t1 = n2 sin t2. Find the refracted angle, the critical angle and total internal reflection. Free.
Lens Magnification Calculator
Solve the thin lens equation 1/f = 1/do + 1/di and find magnification m = -di/do. Enter any two of focal length, object and image distance. Free tool.
555 Timer Calculator
Calculate 555 timer astable frequency, period, high and low times and duty cycle from R1, R2 and the timing capacitor. Free oscillator design helper.
Absolute Humidity Calculator
Calculate absolute humidity in grams of water vapor per cubic meter from air temperature and relative humidity. Fast, free and works in your browser.