How to Convert Carats to Stone (ct to st)
Weight units matter at the wet market, where older stalls and Chinese medical halls still quote prices per kati or tael, and when following American recipes in ounces and pounds. This guide shows how to convert carats into stone by hand, with examples and a quick-reference table.
The conversion
To convert carats to stone, multiply the value by 3.149461e-05. To go the other way, divide by the same number (or multiply by 31,751.4659). Because the factor is tiny, scientific notation keeps the numbers manageable.
Stone = carats × 3.149461e-05
Worked examples
- 3 ct = 9.448383e-5 st
- 12.5 ct = 0.000394 st
- 75 ct = 0.002362 st
Carats to Stone table
| Carats | Stone |
|---|---|
| 1 ct | 3.149461e-5 st |
| 2 ct | 6.298922e-5 st |
| 5 ct | 0.000157 st |
| 10 ct | 0.000315 st |
| 20 ct | 0.00063 st |
| 25 ct | 0.000787 st |
| 50 ct | 0.001575 st |
| 100 ct | 0.003149 st |
| 250 ct | 0.007874 st |
| 500 ct | 0.015747 st |
| 1,000 ct | 0.031495 st |
Common questions
Is ct to st exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Stone to Carats converter.
Mistakes to avoid
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Background
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
For any value, use the Carats to Stone Converter or browse all weight converters.
Run your own numbers: Carats to Stone Converter