Golden ratio calculator
A golden cut makes the whole relate to the larger part as the larger part relates to the smaller. For a canvas, enter one side and the other side is fixed. You do not have to guess it.
Calculator form
How to use
Enter the side you know
A sheet width, the long side of a photo, or a length you want to divide.
Say whether it is long or short
That chooses multiply by φ or divide by φ.
Mark it on the page
The rectangle is the frame. The cut of the long side is a place for the main shape.
Sample calculations
Long side 50 cm
Short side ≈ 30.9 cm. Cut: 30.9 + 19.1 cm
Common mistakes
Mistake
Centering the horizon and calling it golden → The cut sits near 62% of the length, closer to one edge.
FAQ
Which φ is used?
The exact (1 + √5) / 2, about 1.618. Rounding to 1.6 already moves the short side by a few millimeters on a one-meter canvas.
Is this a required composition?
No. It is a useful mark. Leave it if the subject wants a different place.
Lock it in with practice
Open the free editor and apply the result — a short sketch beats more reading.