Precision tools for scale model builders
Convert the dimensions, block the scene, build it. A scale calculator that handles metric and imperial in the same calculation, and a staging tool that shows you the scene from where it will actually be seen.
The tools
Scale Calculator
Enter a real-world dimension and a ratio, get the scaled figure to three decimal places. Input in feet, output in millimetres, or any other combination — the conversion and the scaling happen in one step rather than two. Presets cover architecture, model railroading, diecast, and tabletop scales, and results are drawn against familiar objects at the same scale so you can see whether a number is plausible before you cut.
Open the calculator →Stage
Block out a diorama with proxy volumes, set the dimensions, then look at it from where it will actually be viewed: a shelf above eye level, a competition table you stand over, a display case. Composition overlays are available as optional reference aids.
How scale works
Reading a scale ratio
A scale ratio is a division instruction. In 1:87, one unit on the model represents 87 of the same unit in the real world — 87 millimetres becomes 1 millimetre, 87 feet becomes 1 foot. The units on both sides are always identical, which is what makes the ratio itself unitless and portable between measurement systems.
Written as a fraction, 1/87, it behaves the same way: multiply a real dimension by the fraction to scale down, divide to scale up. Larger denominators mean smaller models. 1:12 is a doll's house; 1:160 fits a mainline locomotive in the palm of your hand.
The ratio tells you nothing about the size of the finished piece on its own. A 1:35 figure is roughly 50 mm tall; a 1:35 tank is roughly 250 mm long. Same scale, very different bench space.
For the four notations that ratio gets written in, why so many of the standard numbers are awkward, and which scales sit close enough to confuse, see Reading scale ratios: notation, awkward numbers, and near-identical scales.
Where mixed units go wrong
Most scale errors are not arithmetic errors. They are unit errors that survive the arithmetic intact.
The common shapes:
- Converting and scaling as separate operations. Reducing 24 feet to 1:48 by first converting to millimetres, then dividing, then rounding to something convenient, then converting again for the ruler you happen to be holding. Each conversion is correct; the accumulated rounding is not.
- Reference material in a system you aren't working in. A drawing dimensioned in inches, a kit moulded to metric, a base cut from imperial stock. Nothing is wrong with any of them individually.
- Ratios that aren't the ones you assume. 1:76 and 1:72 are close enough to look interchangeable in a photograph and far enough apart to be obvious side by side on a shelf. So are 1:48 and 1:43.
The defence is doing the whole conversion in one operation, and keeping full precision until the moment you actually read a number off. Rounding early is where the millimetre goes.
Scale, bases, and display height
Scaled dimensions determine the model. They do not determine the base, and they do not determine what the finished piece looks like to someone standing in front of it.
Base size is a composition decision that starts from the model's footprint and adds working room — space for groundwork, for a second figure, for the eye to settle before it reaches the edge. There is no ratio that produces it.
Display height is the part most often left until the model is finished. A diorama built flat on a bench and then placed on a shelf at 1600 mm is seen from below, at an angle it was never composed for. Elements that read clearly from above disappear behind each other. Nothing about the scale conversion predicts this — it is a function of where the piece ends up, which is why it is worth deciding before the groundwork goes down.