Smartphone Projector Calculator

Find the magnification of a DIY lens projector.

Lens focal length

Phone-to-lens distance

Magnification (×) 2

Lens-to-screen distance 300

Formula: 1/f = 1/d_o + 1/d_i; M = d_i ÷ d_o

Step-by-step with your numbers:

1. Values used:

2. Lens focal length = 100

3. Phone-to-lens distance = 150

5. Magnification = 2×

6. Lens-to-screen distance = 300

Did we solve your problem today?

A single converging lens projects a magnified image of a phone screen onto a wall.

The math behind it

The thin-lens equation 1/f = 1/d_o + 1/d_i gives the image distance; magnification M = d_i ÷ d_o.

100 mm lens, phone at 150 mm → image at 300 mm, 2× magnification.

Why is the image upside down?

A single converging lens flips the image, so you mirror the phone display.