Scaling off Photos - Calculating Scale from Photos

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RULE ONE

You MUST have one known measurement of the vehicle concerned.

RULE TWO

The photo must be a FULL, SQUARE ON side, front or rear shot. The picture used here a full side on photo of my chosen vehicle. Now while this photo is not quite 100% square on, it is so close that it will not matter.

To conform to RULE ONE our one known measurement is the wheelbase (centre of front wheel to centre of rear wheel). In this vehicles case it is 116inches.

So our two rules have been met and complied with. Now print out your photo onto an A4 sheet of paper. I do this as it brings the picture almost to the scale I want to work in, which is 1/35 scale.

Now as I normally work in Metric, I convert the 116 inches to millimeters by multiplying by 25.4 - this is the number of millimeters to an inch.

So….116 multiplied by 25.4 = 2946.4 millimeters.

I drop off the point 4 and convert to meters (divide by 1000). So it becomes 2.946 meters.

I then multiply this by my scale factor which is 28.57 for 1/35 scale.

So….2.946 multiplied by 28.57 = 84.167 millimeters.

I then simplify this by rounding up to 85mm.

So at 1/35 scale our vehicle has a wheelbase of 85 millimeters.

We then measure the wheelbase on the picture with a suitable ruler. Mine worked out to 103 millimeters. Now with our trusty calculator we divide 103 by 85. This gives a factor (result) of 1.211 or to round it up 1.22. I then write this on my picture as this is a constant figure to use in all further calculations on this photo.

From now on you just have to measure any part in the picture and divide that figure by 1.22 and this will give you a pretty close 1/35 scale size of that part. For instance the front doors of the vehicle in my picture measure out to 28.5 millimeters. Divide this by 1.22 and the measurement is 23.3 millimeters.

Scale	Multiply by
1/76	13.16
1/72	13.88
1/48	20.83
1/35	28.57
1/32	31.25
1/24	41.70
1/16	62.50
1/8	125.0
1/4	250.0
By multiplying the real measurement by the above scale ‘factors’ it gives you the correct scale measurement. For Example 1 meter at 1/35 scale is 28.57millimeters long.

You will have to make some adjustments as you build but normally these are only minor. You can work out radius and diameters using this method as well.

I hope this is clear enough for you guys out there as well and it works the same in inches as well.

Cliff Hutchings
9 April 2005

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