Picometre Converter
1 pm = 10⁻¹² m. Every metric scale is shown below.
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The scale of atoms
A picometre is a million millionth of a metre — 10−12. It is the natural unit for atoms and the bonds between them.
1 pm = 1 × 10−12 m
A hydrogen atom is about 106 pm across. A carbon–carbon single bond is 154 pm, a double bond 134, a triple bond 120 — which is how bond order can be read straight off a measured length.
Chemists often prefer the ångström, which is 100 pm, because it puts most bond lengths between 1 and 3. The picometre is the SI-approved equivalent and avoids a non-SI unit.
The picometre
A million millionth of a metre. It is the scale of individual atoms: a hydrogen atom is about 106 pm across, and a carbon–carbon bond is roughly 154 pm.
Chemists often prefer the ångström, which is 100 pm, because it puts most bond lengths between 1 and 3. The picometre is the SI-approved alternative.
The metre
The SI base unit of length. It began in 1793 as one ten-millionth of the distance from the equator to the North Pole, then became a platinum bar, and since 1983 has been defined by the speed of light: the distance light travels in 1/299,792,458 of a second.
That definition makes the metre exact and reproducible anywhere, which is why every other unit on this page is now defined in terms of it — including the foot and the inch.
The working, step by step
Every line updates with whatever you type above. The point is the method, which is the same for any pair of units in this family.
The same quantity, two different numbers
One physical amount, read off two scales. The tick marks do not line up, and the gap between them is the conversion factor made visible.
Your turn
Reading a method and being able to use it are different things. Answer within half a per cent and it counts as correct.
Score: 0 of 0
How to use this converter
- Type into either box. The other side updates as you go; there is no button to press.
- Swap the direction with the button between the boxes, carrying your value across.
- Set the decimals if the default is more or less precision than you need.
- Copy the answer with its unit, ready to paste.
- Use the shortcut buttons for the values that come up most often.
- Share the result. The address bar tracks what you type, so the link you copy opens on the same number.
Common uses and tips
Where length conversions come up
- Height. Quoted in feet and inches in Britain and America, and in centimetres nearly everywhere else. 5 ft 10 in is 178 cm.
- Buying things online from another market, where the dimensions are in units your tape measure does not have.
- DIY and building, where materials come in metric sizes and older plans are in imperial.
- Screens, tyres and pipes, which stay in inches worldwide even in fully metric countries.
- Running and cycling, where race distances are metric and training apps may report either.
Numbers worth carrying
- 1 inch = 2.54 cm exactly. Everything imperial in this family descends from it.
- 1 foot = 30.48 cm, twelve inches.
- 1 yard = 0.9144 m, a little shorter than a metre.
- 1 mile = 1.609 km, and 1 km = 0.621 mile.
- A metre is about 39.37 inches, or 3 ft 3 in.
Mental shortcuts
Kilometres to miles: multiply by six and drop the last digit. 80 km × 6 = 480, drop the digit for 48 miles, against a true 49.7.
Miles to kilometres: add sixty per cent. 50 miles plus 60 % is 80 km, against a true 80.5.
Centimetres to inches: divide by 2.5 and take off a little. Dividing by 2.5 gives an answer about 1.6 % high.
Mistakes worth avoiding
- Feet and inches are not decimal. 5.5 feet is 5 ft 6 in, not 5 ft 5 in. Multiply the decimal part by twelve.
- Do not use length factors for area or volume. A foot is 0.3048 m, but a square foot is 0.0929 m² and a cubic foot 0.0283 m³.
- Check which mile. A nautical mile is 1,852 m, about 15 % longer than a statute mile.
Values people look up most
Each one opens the converter with the number already in it.
- 1 pm to m
- 10 pm to m
- 100 pm to m
- 106 pm to m
- 120 pm to m
- 134 pm to m
- 154 pm to m
- 200 pm to m
- 500 pm to m
- 1,000 pm to m
- 10,000 pm to m
- 1,000,000 pm to m
- 1,000,000,000,000 pm to m
Quick reference
106 pm is a hydrogen atom; 154 pm a carbon–carbon single bond.
| Picometres | Metres |
|---|---|
| 1 pm | 0 m |
| 100 pm | 0 m |
| 106 pm | 0 m |
| 154 pm | 0 m |
| 1,000 pm | 0 m |
| 1,000,000 pm | 0.000001 m |
| 1,000,000,000 pm | 0.001 m |
| 1,000,000,000,000 pm | 1 m |
Questions people ask
How many metres is a picometre?
1 × 10⁻¹² m.
What is an ångström in picometres?
Exactly 100 pm.
How big is an atom in picometres?
Roughly 60 to 300 pm depending on the element. Hydrogen is about 106 pm across.
How many picometres in a nanometre?
Exactly 1,000.