THE SCALE GUIDE

Pick a ratio.
Keep the important parts.

A scale sets the mathematical relationship between an object and its model. Choosing one also means deciding what fits, what remains visible and what deserves extra design attention.

Start with an outside envelope

Measure the real object's maximum length, width and height. Include handles, pipes, antennae and other projections that must remain in the model. These three measurements define a rectangular bounding box. They do not describe the object's shape or its internal spaces.

Next, measure the usable display envelope. A case's external size is usually too generous: subtract its wall thickness, base, cover and the room needed to insert or remove the model. Scale Desk takes the usable space as entered; it does not make these allowances for you.

What “1:50” means

At a ratio of 1:n, every model dimension equals the corresponding real dimension divided by n, using the same unit on both sides. A larger denominator makes a smaller model. A denominator below 1 means enlargement.

Scale Desk first converts measurements to millimetres. One metre is 1,000 mm; one centimetre is 10 mm; one inch is exactly 25.4 mm; one foot is exactly 304.8 mm. It then divides by the scale denominator and converts to your selected output unit. Changing an input-unit selection reinterprets the entered numbers; it does not convert those input numbers automatically.

Find the largest aligned model that fits

Divide each real bounding-box dimension by its corresponding usable display dimension. The largest of these three ratios is the smallest denominator that fits every axis at once.

This calculation assumes that length, width and height remain aligned with the display's matching axes. It does not rotate the box, tilt a model or search for a diagonal fit. A result that just fits has zero spare space on at least one axis. Use a larger denominator or a smaller usable envelope when space is needed around the model.

Work through one example

Take an object measuring 12 × 8 × 6 m and a usable display measuring 300 × 200 × 250 mm. Convert the object to 12,000 × 8,000 × 6,000 mm. The three fit ratios are 40, 40 and 24. Their maximum is 40, so 1:40 gives a 300 × 200 × 150 mm model. Length and width both touch the available limits.

At 1:50, the same object measures 240 × 160 × 120 mm. Subtracting those dimensions from the display leaves 60 × 40 × 130 mm of total spare space. If the box is centred along the length, the 60 mm total becomes 30 mm on each side. The calculator reports total spare space, not a per-side margin.

Check details separately from the envelope

A box can fit while the model still needs redesign. A real 10 mm wall becomes 0.2 mm at 1:50. A narrow rail, unsupported pipe or small letter can also become too delicate or difficult to read. The calculator cannot decide which features should be thickened, simplified, omitted or made as separate parts.

Before manufacture, review material, process, build orientation, feature size, support removal, handling and assembly. Any enlarged feature changes the mathematical model locally. If it projects outside the original envelope, recheck the final outer dimensions.

Use the numbers honestly

The interface rounds ordinary values to three decimal places and uses scientific notation for very large or small values. “Use fit ratio” applies the calculated value at full JavaScript numeric precision. CSV exports also retain numeric precision. The displayed precision is not a claim about measurement accuracy or fabrication tolerance.

The fit comparison allows a relative 10⁻¹² numerical tolerance to avoid floating-point rounding falsely rejecting an exact boundary. This is a computational allowance only. It is much smaller than practical manufacturing clearances.