How do I use this calculator?
Choose a mode to calculate a miniature dimension from a full-size measurement, recover the full-size dimension, or find the scale ratio between corresponding lengths.
Calculator Operations:
- For miniature size, enter the full-size measurement and its unit. Use a scale denominator of 12 for 1:12, or enter another positive denominator, then choose the result unit.
- For full size, enter the miniature measurement and its unit, the scale denominator, and the result unit. At 1:12, the full-size length is 12 times the miniature length.
For scale ratio, enter matching full-size and miniature measurements of the same feature. Their units may differ; the calculator converts them before finding the ratio. These calculations apply to linear dimensions, not areas or volumes.
Use the calculate button when all known values have been entered and use the reset button when you want to clear the values from the calculator.
Convert full-size measurements to 1:12 scale in inches or cm, turn a 1/12 scale model size back into real size, or find the scale ratio of two lengths.
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Calculator Functions
The calculator scales one length at a time, down to a miniature, back up to full size, or from two lengths to the scale between them. Select a function to open it in the calculator.
| Function | Use it when | You enter |
|---|---|---|
| Miniature size from full size | You have a real measurement and need the model size | Full-size measurement, scale denominator and result unit |
| Full size from miniature | You measured a model and want the real size | Miniature measurement, scale denominator and result unit |
| Scale ratio from matching lengths | You know both lengths and want the scale | The same feature measured at full size and on the miniature |
Lengths can be in inches, feet, centimeters, millimeters or meters, and the units may differ. The scale denominator starts at 12. Results also show the full size in feet and inches, and what one full-size foot and meter become.
1/12 Scale Formulas
| X | Scale denominator, 12 for 1:12. A value below 1 means enlargement |
Lengths can be in any one unit. The calculator converts first, using 1 ft = 12 in and 1 in = 2.54 cm [1].
Rearranged, Full size from miniature is full-size length = miniature length × X, and Scale ratio from matching lengths is X = full-size length ÷ miniature length. The answer to the last one shows as 1:X.
1/12 scale in cm and inches
At 1:12, one model inch stands for 12 full-size inches, so 1 inch = 1 foot [2]. In metric, 1 cm on the model stands for 12 cm, so a full-size meter becomes 8.33 cm.
| Full size | 1:12 in inches | 1:12 in cm |
|---|---|---|
| 1 ft | 1 in | 2.54 cm |
| 1 m | 3.28 in | 8.33 cm |
| 180 cm | 5.91 in | 15 cm |
| 6 ft | 6 in | 15.24 cm |
| 2 m | 6.56 in | 16.67 cm |
| 12 ft | 12 in | 30.48 cm |
Limits of This Estimate
- The ratio applies to lengths only. Area changes by the square of the scale factor and volume by its cube, so at 1:12 an area is 144 times smaller and a volume 1,728 times smaller.
- For Scale ratio from matching lengths, measure the same feature on both objects. Displayed results are rounded, and the calculation keeps the unrounded values.
Sources
- NIST, Guide to the SI (SP 811), Appendix B.8: inch and foot definitions
- U.S. Fire Administration (FEMA), Using Engineer and Architect Scales: 1 inch = 1 foot as a drawing scale
