To convert mils to chains, multiply by 1.262626263e-06. That factor is the whole relationship: both units measure length, so the conversion is a proportion with no offset and no substance-specific constant.
Sixty-six feet — the length of a cricket pitch, and the unit the US Public Land Survey was laid out in. One thousandth of an inch, the standard thickness unit for plastic film and PCB traces.
The mil and the millimetre are not the same thing and are out by a factor of about forty. A mil is one thousandth of an inch — 0.0254 mm — and a spec sheet that quotes film thickness in mils means the small unit. British drawings write the same size as "thou". The tables underneath give both a plain step-by-step lookup and a list of real quantities expressed in chains, so you can sanity-check whether your answer is a plausible size.
The formula
mils- The amount you are converting, in mils
1.26262626263e-06- The exact number of chains in one mil
chains- The converted result
How it works, step by step
- Enter the value in mils.
- It is multiplied by 1.26262626263e-06, the exact factor between the two units.
- The answer is shown in chains, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A door height: 8e+04 mil in chains
Take a door height, roughly 8e+04 mil. The conversion is a single multiplication — 8e+04 × 1.26263e-06 — giving 0.10101 ch. Because the relationship is proportional, doubling the input doubles the answer to 0.20202 ch.
A credit card’s long edge: 3370 mil in chains
At 3370 mil (a credit card’s long edge), the same quantity in chains is 3370 × 1.26263e-06 = 0.00425505 ch. One mil is 1.26263e-06 chains, so the numbers shrink as expected.
How to read your score
Frequently asked questions
How many chains are in one mil?
Exactly 1.26262626263e-06. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert mils to chains?
chains = mils × 1.26262626263e-06. Reversed, mils = chains ÷ 1.26262626263e-06, which is the same as multiplying by 792,000.
Which is the bigger unit, the mil or the chain?
The chain. One mil is only 1.26263e-06 of a chain, so it takes 792,000 mils to make one chain.
What does this quantity actually measure?
Both units measure length. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a mil?
One thousandth of an inch, the standard thickness unit for plastic film and PCB traces.
What is a chain?
Sixty-six feet — the length of a cricket pitch, and the unit the US Public Land Survey was laid out in.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Is there a quick way to do mil to ch in my head?
Plenty of people do this in their head: divide by 800,000 instead of using the exact factor 0.000001. At 100 that shortcut gives 0.000125 chains, off by 0.000001 chains or about 1.00%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Mils to chains reference tables
| Mils | Chains |
|---|---|
| 0.5 mil | 6.31313e-07 ch |
| 1 mil | 1.26263e-06 ch |
| 2 mil | 2.52525e-06 ch |
| 3 mil | 3.78788e-06 ch |
| 5 mil | 6.31313e-06 ch |
| 10 mil | 1.26263e-05 ch |
| 20 mil | 2.52525e-05 ch |
| 25 mil | 3.15657e-05 ch |
| 50 mil | 6.31313e-05 ch |
| 75 mil | 9.4697e-05 ch |
| 100 mil | 0.000126263 ch |
| 250 mil | 0.000315657 ch |
| 500 mil | 0.000631313 ch |
| 1000 mil | 0.00126263 ch |
| 5000 mil | 0.00631313 ch |
Exact factor: 1 mil = 1.26262626263e-06 chains.
| Quantity | mil | ch |
|---|---|---|
| A credit card’s long edge | 3370 mil | 0.004255 ch |
| A door height | 8e+04 mil | 0.101 ch |
| An Olympic pool | 1.969e+06 mil | 2.485 ch |
| The Eiffel Tower | 1.299e+07 mil | 16.4 ch |
| A marathon | 1.661e+09 mil | 2098 ch |
| Earth’s diameter | 5.017e+11 mil | 6.334e+05 ch |
Published reference values, converted with the same factor this page uses.