How to convert cm to inches and back, with a table

Centimetres and inches turn up in the same week for most people in the UK. A shop lists a shelf in centimetres, a television is sold by the inch, a pattern asks for a seam allowance in inches, and someone asks how tall you are in feet. The good news is that the two units are linked by one exact number, so you never need to guess. This guide gives you that number, a reference table you can scan, worked examples for everyday jobs, and the rounding habits that stop small errors from adding up.

By Valtrinity. Updated 18 October 2026.

The one number you need: 2.54

Since 1959 the inch has been defined as exactly 2.54 centimetres. That is not a rounded figure or an approximation. It is the definition, agreed between the UK, the USA and other countries, so every conversion between the two units comes down to multiplying or dividing by 2.54.

To go from inches to centimetres, multiply by 2.54. To go from centimetres to inches, divide by 2.54. If you would rather multiply, you can use 0.3937, which is 1 divided by 2.54 and rounded to four decimal places. Both routes give the same answer to the precision most jobs need.

A useful memory aid is that an inch is a little over two and a half centimetres, so a length in centimetres is always a bit more than twice its length in inches, and about two and a half times as large. If your answer does not fit that pattern, you have probably multiplied when you should have divided.

How to convert cm to inches, step by step

Take the length in centimetres and divide it by 2.54. Suppose a picture frame is 45 cm wide. 45 divided by 2.54 is 17.72, so the frame is about 17.7 inches wide. If you are working in your head, divide by 2.5 for a quick estimate (45 divided by 2.5 is 18) and then remember that the true answer is slightly lower.

For a longer length, the same rule applies. A worktop of 240 cm is 240 divided by 2.54, which is 94.49 inches. If the next question is how many feet that is, divide the inches by 12: 94.49 divided by 12 is 7.87 feet, which is 7 feet and about 10.5 inches (0.87 of a foot is 10.4 inches).

Keep the unit attached to each number as you work. Writing 45 cm divided by 2.54 cm per inch makes it clear that the centimetres cancel and leave inches, and it helps you spot the common slip of dividing when you meant to multiply.

How to convert inches to cm

Multiply by 2.54. A 32 inch television is 32 times 2.54, which is 81.28 cm. A 6 inch nail is 15.24 cm long. A 0.5 inch seam allowance is 1.27 cm.

Most people only need a centimetre or a millimetre of precision. In those cases rounding 81.28 cm to 81 cm, or 15.24 cm to 15.2 cm, is fine. If you are cutting something to fit a gap, round in the direction that keeps the part from being too big: round the part down, or round the gap up, and then measure again before you cut.

Fractions of an inch are common on tape measures, such as 3/8 or 5/16. Change the fraction to a decimal first (3 divided by 8 is 0.375) and then multiply. So 3/8 of an inch is 0.375 times 2.54, which is 0.95 cm, or 9.5 mm.

A quick reference table

These figures are rounded to two decimal places. Centimetres to inches: 1 cm is 0.39 in, 2 cm is 0.79 in, 5 cm is 1.97 in, 10 cm is 3.94 in, 15 cm is 5.91 in, 20 cm is 7.87 in, 25 cm is 9.84 in, 30 cm is 11.81 in, 50 cm is 19.69 in and 100 cm is 39.37 in.

Inches to centimetres: 1 in is 2.54 cm, 2 in is 5.08 cm, 3 in is 7.62 cm, 6 in is 15.24 cm, 12 in is 30.48 cm, 24 in is 60.96 cm, 36 in is 91.44 cm and 72 in is 182.88 cm.

Notice that 12 inches, one foot, is 30.48 cm, and 36 inches, one yard, is 91.44 cm. The yard is just under a metre, and a metre is about 39.37 inches, roughly 3 inches more than a yard. That is why a one metre ruler is a little longer than a yard stick.

Height in feet and inches

Height is the conversion people ask for most. To change centimetres to feet and inches, first divide by 2.54 to get total inches, then split the result into whole feet and leftover inches. Take 175 cm: 175 divided by 2.54 is 68.90 inches. 68.90 divided by 12 is 5 with a remainder of 8.90, so 175 cm is 5 feet 8.9 inches, which people usually round to 5 ft 9.

The other way round, multiply the feet by 12, add the inches, and then multiply by 2.54. A height of 5 ft 10 is 5 times 12 plus 10, which is 70 inches. 70 times 2.54 is 177.8 cm. A height of 6 ft 2 is 74 inches, which is 187.96 cm, or about 188 cm.

Some more examples to check your working against: 160 cm is 5 ft 3 (62.99 inches); 170 cm is 5 ft 7 (66.93 inches); 180 cm is 5 ft 10.9, close to 5 ft 11 (70.87 inches); and 190 cm is 6 ft 2.8, close to 6 ft 3 (74.80 inches).

Screens, furniture and clothing

Television and monitor sizes are quoted as a diagonal measurement in inches, even in shops that otherwise use metric. A 55 inch screen has a diagonal of 139.7 cm. Because that is the diagonal, the width is smaller: for a standard 16 to 9 screen the width is about 87 per cent of the diagonal, which is roughly 122 cm for a 55 inch set. Always check the width in the specification before you buy a stand or a cabinet.

Furniture is usually listed in centimetres in the UK, but older items, curtains and some imports use inches. A bed described as 4 ft 6 is 54 inches, or 137.16 cm, which is the standard UK double. A 3 ft single is 36 inches, or 91.44 cm.

Clothing is less simple. Waist and inside leg are often given in inches, such as a 32 inch waist, which is 81.28 cm. Sizes can vary between brands, so use the conversion to compare measurements you have taken yourself with the size chart, rather than relying on the label alone.

Mistakes that cause wrong answers

The most common mistake is using the wrong operation. If you are unsure, think about which unit gives the bigger number. An inch is bigger than a centimetre, so a length has fewer inches than centimetres. If your result in inches is larger than the number of centimetres, you have multiplied by 2.54 instead of dividing.

The second is rounding too early. If you round 2.54 to 2.5 or 3 in the middle of a calculation, the error grows with the length. Over 200 cm, using 2.5 instead of 2.54 changes the answer by more than an inch. Keep the exact figure until the last step and round only the result.

The third is mixing up diagonal and straight-line measurements, or inches and millimetres on a technical drawing. Check which unit the figure is in before you convert, and write the unit next to every number in your notes.

Tools mentioned in this guide

Frequently asked questions