Drawing scale calculator
The reference on screen is 15 cm and the sheet is 45 cm. The percentage comes from the long side, and the short side follows. The frame does not stretch.
Calculator form
How to use
Measure the reference
Width and height of the photo, sketch or object. Any unit, as long as it is the same unit.
Set the target long side
The larger side of the sheet or canvas you are moving onto.
Read the percentage
300% means every distance on the reference is multiplied by three.
Sample calculations
15×10 with a long side of 45
300%, finished size 45×30
Common mistakes
Mistake
Multiplying width and height by different numbers → One factor for both sides, or a circle becomes an oval.
FAQ
What if the target is smaller than the reference?
The percentage drops below 100. The formula is the same: target long side divided by reference long side.
Does this work with a grid?
Yes. Get the overall scale first, then divide both pictures into the same number of cells.
Lock it in with practice
Open the free editor and apply the result — a short sketch beats more reading.