A surveyor's chain is 66 feet.
Chains to Millimeters Converter — ch to mm
Convert Chain (ch) to Millimeter (mm) using the exact conversion factor (1 chain = 20,116.8 millimeter). See the formula, worked examples, conversion table, history, and common uses.
Chains to Millimeters converter
Converter
Length Converter
Convert SI, imperial, US customary, astronomical, scientific, and historical length units.
Context values
Some unit families need one extra value for a physically accurate result.
Millimeter is 0.001 meter units.
Result = input x 20.1168 / 0.001.
Length uses the meter as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Chains to Millimeters
Chain and Millimeter both measure length. Specifically: A surveyor's chain is 66 feet, and millimeter is 0.001 meter units.
Formula
millimeters = chains × 20116.8
This factor comes from each unit's defined relationship to the category's base unit: 1 chain equals 20.1168 base units, and 1 millimeter equals 0.001 base units, so dividing one by the other gives the direct chain-to-millimeter factor of 20116.8.
Simple example
1 ch × 20116.8 = 20,116.8 mm
1 chain = 20,116.8 millimeters.
Real-world example
10 ch × 20116.8 = 201,168 mm
10 chains = 201,168 millimeters.
Conversion table
| Chain (ch) | Millimeter (mm) |
|---|---|
| 1 ch | 20,116.8 mm |
| 5 ch | 100,584 mm |
| 10 ch | 201,168 mm |
| 21.0975 ch | 424,414.188 mm |
| 42.195 ch | 848,828.376 mm |
| 100 ch | 2,011,680 mm |
Reverse conversion: Millimeter to Chain
1 mm × 0.00004970969538 = 0.0000497097 ch
1 millimeter = 0.0000497097 chains.
chains = millimeters × 0.000049709695379
For a page dedicated to this direction, see Millimeter to Chain.
Understanding the Chain (ch)
A surveyor's chain is 66 feet.
Understanding the Millimeter
Millimeter (mm) measures distance. A millimeter is one-thousandth of a meter. It is classified as a SI derived (metric prefix) unit.
Where it's used: Standard small/precision length unit worldwide, including in US engineering and manufacturing
Uses of the Millimeter today
- Engineering drawings and manufacturing tolerances worldwide (including in the US)
- Rainfall measurement in most countries
- Small-scale everyday measurement (screen sizes, hardware)
History of the Millimeter
The millimeter follows from the meter via the 'milli-' SI prefix (10⁻³). It is notable as one of the few metric units in routine US technical/engineering use, since precision manufacturing and electronics are often specified in millimeters even in the US.
Historical origin. Millimeter was not the invention of a single named person; it developed through the process described above.
Millimeter — sources
- BIPM SI Brochure — SI prefixes — Defines 'milli-' as the prefix for 10⁻³.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many millimeters are in 1 chain?
1 chain equals 20,116.8 millimeters, using the exact defined conversion factor rather than an estimate.
How do I convert chain to millimeter?
Multiply the chain value by 20116.8. The converter above does this instantly to whatever precision you set.
How do I convert millimeter back to chain?
Use the reverse factor: 1 millimeter equals 0.0000497097 chains. You can also use the swap control in the converter above to flip the direction instantly.
What is a chain?
Chain (ch) is a unit of length.
What is a millimeter?
Millimeter (mm) measures distance. A millimeter is one-thousandth of a meter. It is classified as a SI derived (metric prefix) unit.
Is the chain to millimeter conversion exact?
Yes. Both chain and millimeter are defined by fixed standards rather than physical artifacts, so the factor of 20116.8 used above is exact to as many digits as you choose to display.