Scale Model Conversion Calculator
Convert between real-world size and scale-model size for any scale ratio — pick a named scale (HO, N, 1:35, 1:48, 1:72…) or enter a custom ratio, and convert a size directly between two different scales.
Input
What are you trying to calculate?
The dimension you already have — a real-world length or an existing model's size.
The scale ratio 1:N — pick a named hobby/architectural scale or use a custom one.
Output
| Metric | Value |
|---|---|
| No data yet | |
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/scale-model-conversion-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"mode": "toModel",
"value": "40",
"valueUnit": "in",
"scale": "24",
"outputUnit": "in"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `scale-model-conversion-calculator` tool (Scale Model Conversion Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/scale-model-conversion-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="Scale Model Conversion Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
The Scale Model Conversion Calculator converts a dimension between real-world size and scale-model size for any scale ratio (1:N) — or, if you already have a part sized for one scale, works out the equivalent size at a different scale entirely.
How to use it
Real-world size → Model size (default):
- Enter the real-world dimension and its unit (mm, cm, m, in, ft or yd).
- Pick a scale — choose a named preset (HO 1:87, 1:35 military, 1:48 aircraft, 1:24 diecast, and more) or select "Custom ratio…" and type the
Nin1:Nyourself. - Read the model size in whichever unit you want it shown in.
Model size → Real-world size: switch "Direction" to this mode, enter the model's measured size and the scale it was built at, and read the real-world size it represents.
Convert between two scales: enter a size you already have (a kit part, a 3D-print, a scratch-built piece), the scale it was made for, and the scale you want the equivalent size for — the calculator round-trips it through the real-world size for you.
Why a preset library instead of a bare ratio field?
Most modeling scales are referred to by name more often than by their raw ratio — a railway modeler thinks "HO" or "N scale," not "1:87" or "1:160." This tool's scale picker lists the common named scales across model railways (HO, OO, N, Z, G), military/armor (1:35, 1:72), aircraft (1:32, 1:48, 1:72, 1:144), diecast cars (1:18, 1:24, 1:43, 1:64), ships (1:700) and common architectural fractional scales (1/4"=1'-0", 1/8"=1'-0") — so you can pick the scale you actually work in without having to already know its ratio. A "Custom ratio…" option covers anything not on the list.
What does "1:N" mean?
A scale of 1:N means one unit of length on the model equals N of the same unit in reality — a 1:87 (HO) model that measures 10 mm represents 870 mm (0.87 m) in real life. The ratio holds for any unit, which is why scales are stated this way rather than tied to a specific unit pair.
How does scale-to-scale conversion work?
The size you enter is first converted to its real-world equivalent using the "from" scale, then that real-world size is divided by the "to" scale's ratio — the same two steps you'd do by hand, just without re-typing the intermediate real-world number or converting units yourself.
Is my data private?
Yes. Every calculation runs entirely in your browser — nothing is uploaded to a server.
Common uses
Sizing a 3D-printed or scratch-built part to match an existing kit's scale, checking whether a diecast car and a display case are compatible scales, converting a blueprint or architectural drawing dimension into a dollhouse or display-model size, or working out how big a real object was from a measured model.
Working with real-world map distances instead of models? Use the Map Scale Calculator. Scaling ingredient quantities rather than physical dimensions? Try the Recipe Scale Calculator.