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Centimetres to Inches
To convert centimetres to inches, divide by 2.54, because an inch is exactly 2.54 cm. 30 cm ÷ 2.54 = 11.81 inches. On a ruler marked in sixteenths that is 11 13/16 inches, which is within 0.04 mm of 30 cm. The converter gives the decimal, the ruler mark and feet and inches.
Type centimetres.
| Shown as | Value |
|---|---|
| Inches | 11.81 in |
| Nearest 1/16 inch, as a ruler reads | 11 13/16 in (0.04 mm over) |
| Nearest 1/32 inch | 11 13/16 in (0.04 mm over) |
| Nearest 1/64 inch | 11 13/16 in (0.04 mm over) |
| Feet and inches | 0 ft 11.8 in |
| Millimetres | 300 mm |
| Metres | 0.3 m |
The figures above are an example: put in your own. A decimal comma (2,5) works too. Worked out in this browser and kept there; nothing is sent anywhere.
Type a length in centimetres and read it in inches as a decimal, as the nearest sixteenth of an inch you can find on a ruler, and in feet and inches. The chart below covers the lengths people look up most.
Centimetres to inches is a division by 2.54. The centimetre is a hundredth of a metre; the inch, by the 1959 international agreement, is exactly 2.54 of them.
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Key facts
| Detail | Answer |
|---|---|
| Formula | inches = cm ÷ 2.54 |
| Example | 30 cm = 11.81 in = 11 13/16 in on a ruler |
| 1 cm | 0.3937007874… in (never ends) |
| Quick estimate | Divide by 2.5: 1.6% too high |
| A4 paper | 21 × 29.7 cm = 8.27 × 11.69 in |
| Where your numbers are kept | This browser only |
How to convert centimetres to inches
Divide, round, then find the mark.
Measure in centimetres
Read to the millimetre if you can: 29.7, not 30.
Divide by 2.54
29.7 ÷ 2.54 = 11.69 inches.
Round to what you need
Two decimal places is a hundredth of an inch, finer than a tape reads.
Find the ruler mark
Multiply the decimal part by 16 and round: 0.69 × 16 = 11, so 11/16.
Check the size
Inches should be a smaller number than centimetres, about 40% of it.
Who converts centimetres to inches
People with a metric measurement and an imperial ruler, shop or reader.
Online shoppers
A European listing in cm, a US space in inches.
Sewers and knitters
A pattern in cm, a tape in inches.
Printers and designers
A4 and A5 page sizes against US Letter.
Parents
A baby’s length from the midwife, for relatives in the US.
Travellers
Cabin bag limits given in cm by one airline and inches by another.
Students
Homework that asks for the answer in inches.
Centimetres on an inch ruler: the nearest sixteenth
Converting centimetres to inches gives a decimal: 30 cm is 11.81 inches. But almost nobody measures in decimal inches. A ruler, a tape and a sewing tape in the US are marked in halves, quarters, eighths and sixteenths, so a decimal like 11.81 has to be turned into a mark you can find. The converter does that: 30 cm is 11 13/16 inches, and the 13/16 mark is 0.04 mm longer than 30 cm, closer than anyone can read a tape.
| Centimetres | Inches (2 decimals) | Nearest 1/16 inch, and the gap |
|---|---|---|
| 1 cm | 0.39 in | 3/8 in (0.48 mm under) |
| 2 cm | 0.79 in | 13/16 in (0.64 mm over) |
| 2.5 cm | 0.98 in | 1 in (0.4 mm over) |
| 5 cm | 1.97 in | 1 15/16 in (0.79 mm under) |
| 10 cm | 3.94 in | 3 15/16 in (0.01 mm over) |
| 15 cm | 5.91 in | 5 7/8 in (0.78 mm under) |
| 20 cm | 7.87 in | 7 7/8 in (0.03 mm over) |
| 25 cm | 9.84 in | 9 13/16 in (0.76 mm under) |
| 30 cm | 11.81 in | 11 13/16 in (0.04 mm over) |
| 50 cm | 19.69 in | 19 11/16 in (0.06 mm over) |
| 60 cm | 23.62 in | 23 5/8 in (0.08 mm over) |
| 75 cm | 29.53 in | 29 1/2 in (0.7 mm under) |
| 100 cm | 39.37 in | 39 3/8 in (0.13 mm over) |
| 150 cm | 59.06 in | 59 1/16 in (0.19 mm over) |
Two things in that table surprise people. A 30 cm ruler is not a foot: it stops 3/16 of an inch short of the 12-inch mark, which is why metric and imperial rulers that look the same size are not interchangeable for anything that must fit. And 2.5 cm, often treated as “an inch”, is 0.4 mm (about 1/64 inch) short of one, a gap that adds up: ten of them make 25 cm, which is 9.84 inches, not 10.
Why dividing by 2.5 is not good enough
The factor is 2.54 and nothing else: an inch has been exactly 2.54 cm since 1959. Most wrong answers come from using a rounder number, or from the direction.
| Method | Gives | Right answer | Off by |
|---|---|---|---|
| Divide by 2.54 | 39.37 in | 39.37 in | Nothing |
| Divide by 2.5 | 40 in | 39.37 in | 0.63 in (1.6%) |
| Multiply by 0.4 | 40 in | 39.37 in | 0.63 in (1.6%) |
| Multiply by 0.39 | 39 in | 39.37 in | 0.37 in (0.9%) |
| Multiply by 2.54 (wrong way) | 254 in | 39.37 in | Six and a half times too big |
A quick check catches the wrong-way slip: an inch is the bigger unit, so the number of inches must be smaller than the number of centimetres, by a factor of about two and a half. Dividing by 2.5 is a fair estimate in your head, but it is 1.6% high, which on a 180 cm sofa is over an inch too wide for the alcove you measured.
The decimal never ends. 1 cm is 50/127 of an inch, and because 127 is prime the digits of 0.3937007874… repeat only every 42 places. Any figure in inches from a whole number of centimetres is therefore rounded, and the converter says to how many places.
Paper, clothing and luggage in both units
Centimetres become inches most often when something measured in a metric country has to fit something sold or described in an imperial one. These are the cases where the conversion decides a purchase.
| Item | In cm | In inches | Watch for |
|---|---|---|---|
| A4 paper | 21 × 29.7 | 8.27 × 11.69 | Not US Letter, 8.5 × 11 in |
| Waist on an EU size label | 81 | 31.89 | Labelled W32: clothing sizes are rounded |
| Laptop sleeve, inner width | 36 | 14.17 | Check the laptop body, not its screen size |
| Picture frame, 30 × 40 cm | 30 × 40 | 11.81 × 15.75 | Not a 12 × 16 in frame |
| Baby length at birth | 50 | 19.69 | Often written 19.7 in |
| Cabin bag limit | 55 × 40 × 20 | 21.65 × 15.75 × 7.87 | Airlines round, the gauge does not |
Paper sizes come from ISO 216, which defines A4 as 210 × 297 mm. Its inch equivalent, 8.27 × 11.69 inches, is not a US paper size, and a document set up for one prints with a margin shifted on the other. For a page of text, the words per page calculator lets you pick either sheet.
What this converter does not do
This converts centimetres to inches. For a height, where the answer is wanted in feet and inches and rounding to a whole inch matters, use the height converter; for millimetres from a tape or drawing, the millimetre to inch converter also gives 1/32 and 1/64 marks and thousandths. Areas such as square centimetres need the factor squared (6.4516 cm² to the square inch) and are not converted here. Entries up to a billion centimetres are accepted; negative lengths are refused.
This converter or a decimal-only one
What this page adds to a typical one-formula converter.
| This converter | A typical converter | |
|---|---|---|
| Ruler marks | Nearest 1/16, 1/32 and 1/64 inch, each with the gap | Decimal inches only |
| Exact or rounded | Says which, exact digits shown | Unlabelled rounding |
| Feet and inches | Given for long lengths | Not given |
| Decimal comma | 2,5 read as 2.5 | Often an error |
| Your entries leave the browser | Never | Varies |
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Frequently asked questions
How many inches is 30 cm?
30 cm is 11.81 inches (11.811… exactly), or 11 13/16 inches to the nearest sixteenth. That is why a 30 cm ruler is about 3/16 of an inch shorter than a 12-inch ruler. In feet and inches it is 0 ft 11.8 in, just under a foot.
How do you convert cm to inches?
Divide the number of centimetres by 2.54. 50 cm ÷ 2.54 = 19.69 inches. If you need a ruler mark, multiply the decimal part by 16 and round to the nearest whole number: 0.69 × 16 is about 11, so 19 11/16 inches.
Is 2.5 cm equal to 1 inch?
No, it is a little short. An inch is exactly 2.54 cm, so 2.5 cm is 0.984 inches, 0.4 mm (about 1/64 inch) less than a full inch. The gap is small once but grows with length: 100 cm is 39.37 inches, not the 40 that the 2.5 shortcut gives.
How many cm make an inch?
Exactly 2.54 centimetres make one inch. This was fixed on 1 July 1959, when the US, UK, Canada, Australia, New Zealand and South Africa agreed on a yard of exactly 0.9144 metres, from which the inch follows as 25.4 mm. Before that, the US and UK inches differed very slightly.
What is 1 cm in inches as a fraction?
Exactly 50/127 of an inch, which is 0.3937 as a decimal. On a ruler marked in sixteenths, the nearest mark is 6/16, which reduces to 3/8 inch, about 0.48 mm short of a centimetre. On a ruler marked in thirty-seconds it is 13/32, 0.32 mm over.
How do I convert cm to inches in my head?
Multiply by 4 and divide by 10, which is the same as dividing by 2.5. It overstates by 1.6%. For a closer figure, take off one part in sixty of the result: 100 cm gives 40, less two-thirds, about 39.3 inches against the true 39.37.
How many inches is A4 paper?
A4 is 210 × 297 mm, which is 8.27 × 11.69 inches. US Letter is 8.5 × 11 inches, so A4 is about a quarter of an inch narrower and nearly three-quarters of an inch taller. A4 comes from ISO 216; Letter is a North American size.
How many inches are in a metre?
One metre is 39.37 inches (39.3700787… exactly), which is 3 ft 3.37 in. A yard is 36 inches, so a metre is about 3.4 inches longer than a yard. To convert metres to inches, multiply by 100 and divide by 2.54.
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