This page converts parsecs into millimeters using the factor 3.085677581e+19, and shows the reverse figure alongside it. Both units measure length, which is why one number does the whole job.
The distance at which one astronomical unit subtends one arcsecond: about 3.26 light-years. One thousandth of a metre — the finest gradation on a standard ruler.
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 millimeters, so you can sanity-check whether your answer is a plausible size.
The formula
parsecs- The amount you are converting, in parsecs
3.08567758149e+19- The exact number of millimeters in one parsec
millimeters- The converted result
How it works, step by step
- Enter the value in parsecs.
- It is multiplied by 3.08567758149e+19, the exact factor between the two units.
- The answer is shown in millimeters, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A larger figure: 100 pc in millimeters
Take a larger figure, roughly 100 pc. The conversion is a single multiplication — 100 × 3.08568e+19 — giving 3.08568e+21 mm. Because the relationship is proportional, doubling the input doubles the answer to 6.17136e+21 mm.
A round figure: 1 pc in millimeters
Take a round figure, roughly 1 pc. The conversion is a single multiplication — 1 × 3.08568e+19 — giving 3.08568e+19 mm. Because the relationship is proportional, doubling the input doubles the answer to 6.17136e+19 mm.
How to read your score
Frequently asked questions
How many millimeters are in one parsec?
Exactly 3.08567758149e+19. 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 parsecs to millimeters?
millimeters = parsecs × 3.08567758149e+19. Reversed, parsecs = millimeters ÷ 3.08567758149e+19, which is the same as multiplying by 3.24077928944e-20.
Which is the bigger unit, the parsec or the millimeter?
The parsec. One parsec equals 3.08568e+19 millimeters.
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 parsec?
The distance at which one astronomical unit subtends one arcsecond: about 3.26 light-years.
What is a millimeter?
One thousandth of a metre — the finest gradation on a standard ruler.
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 pc to mm in my head?
Plenty of people do this in their head: multiply by 3.0000e+19 instead of using the exact factor 3.0857e+19. At 100 that shortcut gives 3.0000e+21 millimeters, off by 8.5678e+19 millimeters or about 2.78%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Parsecs to millimeters reference tables
| Parsecs | Millimeters |
|---|---|
| 0.5 pc | 1.54284e+19 mm |
| 1 pc | 3.08568e+19 mm |
| 2 pc | 6.17136e+19 mm |
| 3 pc | 9.25703e+19 mm |
| 5 pc | 1.54284e+20 mm |
| 10 pc | 3.08568e+20 mm |
| 20 pc | 6.17136e+20 mm |
| 25 pc | 7.71419e+20 mm |
| 50 pc | 1.54284e+21 mm |
| 75 pc | 2.31426e+21 mm |
| 100 pc | 3.08568e+21 mm |
| 250 pc | 7.71419e+21 mm |
| 500 pc | 1.54284e+22 mm |
| 1000 pc | 3.08568e+22 mm |
| 5000 pc | 1.54284e+23 mm |
Exact factor: 1 parsec = 3.08567758149e+19 millimeters.
| Quantity | pc | mm |
|---|---|---|
| A credit card’s long edge | 2.774e-18 pc | 85.6 mm |
| A door height | 6.585e-17 pc | 2032 mm |
| An Olympic pool | 1.620e-15 pc | 5e+04 mm |
| The Eiffel Tower | 1.069e-14 pc | 3.3e+05 mm |
| A marathon | 1.367e-12 pc | 4.22e+07 mm |
| Earth’s diameter | 4.129e-10 pc | 1.274e+10 mm |
Published reference values, converted with the same factor this page uses.