scaling up a painting

[razman]

Hi, I have a small drawing of a galleon that is 3 inches on the waterline with a mast height of 5 and a half inches. I want to transfer this to a painting with a waterline of approximately 10 inches, what should the mast height be?. Is there an easy formula that I could use for future use? or am I in the wrong topic section? Thanks

[Jugglering]

The ratio of the mast height to the waterline in the small drawing is 5.5 to 3. You want the waterline to be 10", so keeping the ratio the same, the answer would be 5.5/3 x 10 = 18.3".

[wildwood]

plus.... if you're using a computer to increase the size, make sure the 'keep ratio aspect the same' option is ticked and increase the image by 333%.
That should automatically increase the height and width in the right proportions.

[razman]

Thankyou juggerling and wildwood, just one question from this maths ignoramus, where would I find the ratios you mention, on the computer?, Is there a dedicated website for this sort of problem?or should I go back to school which I left many many moons ago?.