Comparing heights: units, scale and what the gap means
How feet and inches convert to centimetres exactly, how to read a height difference in cm, inches and per cent, and how the comparison chart is drawn to scale.
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In short
- An inch is exactly 2.54 cm and a foot exactly 30.48 cm, so a height in feet and inches converts to centimetres with no rounding until the end.
- At 175 cm and 160 cm the gap is 15 cm, or 5.9 inches. The taller person is 9.4% taller, while the shorter is 8.6% shorter, because each percentage is measured from a different height.
- In the chart every head touches the grid line for its own height, so heights are to scale. The figures' widths are not.
- The world's average adult man born in 1996 is 171 cm, and the average woman 159 cm.
A height comparison answers a simple question — how much taller is one person than another? — and then a picture answers it better than a number can. This page explains the arithmetic behind the tool: converting between feet and centimetres without drift, the three ways a difference can be written, and how the chart keeps every figure to scale.
Feet, inches and centimetres
Heights in India are written both ways. A doctor's chart, a passport and most forms use centimetres; ask someone their height and they will usually say five feet something. The two convert exactly, because since the late 1950s the inch has been defined as exactly 25.4 millimetres. So:
- 1 inch = 2.54 cm, exactly.
- 1 foot = 12 inches = 30.48 cm, exactly.
To convert a height in feet and inches to centimetres:
cm = (feet × 12 + inches) × 2.54
So 5 feet 8 inches is (5 × 12 + 8) × 2.54 = 68 × 2.54 = 172.72 cm. Going the other way, divide by 2.54 to get inches, then take out whole feet: 175 cm is 175 ÷ 2.54 = 68.9 inches, which is 5 feet 8.9 inches.
| Feet and inches | Centimetres | Centimetres | Feet and inches | |
|---|---|---|---|---|
| 4′ 10″ | 147.32 | 150 | 4′ 11.1″ | |
| 5′ 0″ | 152.40 | 155 | 5′ 1″ | |
| 5′ 2″ | 157.48 | 160 | 5′ 3″ | |
| 5′ 4″ | 162.56 | 165 | 5′ 5″ | |
| 5′ 6″ | 167.64 | 170 | 5′ 6.9″ | |
| 5′ 8″ | 172.72 | 175 | 5′ 8.9″ | |
| 5′ 10″ | 177.80 | 180 | 5′ 10.9″ | |
| 6′ 0″ | 182.88 | 185 | 6′ 0.8″ | |
| 6′ 2″ | 187.96 | 190 | 6′ 2.8″ |
The tool keeps the exact figure and rounds only for display, to a tenth of a centimetre or a tenth of an inch. Switching between the two units never changes anyone's height: 5′ 9″ is 175.26 cm, shown as 175.3, and switching back shows 5′ 9″ again. For other lengths, the Unit Converter handles metres, feet, inches and more.
Three ways to write a difference
Say Rahul is 175 cm and Priya is 160 cm. The difference can be written three ways, and each answers a slightly different question.
In centimetres or inches. 175 − 160 = 15 cm. In inches that is 15 ÷ 2.54 = 5.9 inches. This is the plain gap, the same whichever way round you say it.
As "taller by" a percentage. Rahul is 15 cm taller than a height of 160 cm, so he is 15 ÷ 160 = 9.4% taller. The percentage is measured against the shorter person, because that is what "taller than Priya" is compared with.
As "shorter by", or a share of the tallest. Priya is 15 cm shorter than a height of 175 cm, so she is 15 ÷ 175 = 8.6% shorter. Put the other way, her height is 160 ÷ 175 = 91.4% of his.
That is not a contradiction: 9.4% taller and 8.6% shorter describe the same 15 cm, measured from two different starting heights. The tool's headline uses "taller by", and its table shows each person as a percentage of the tallest, so both readings are there.
With more than two people, everyone is measured against the tallest, which gives one fixed reference instead of a tangle of pairs. The headline shows the range from tallest to shortest.
How the chart is drawn to scale
Every figure stands on the same ground line, and the vertical scale is the same for all of them. The chart picks its own top: a round number at least 14% above the tallest height, so there is room to print the name and height over the tallest head. For 175 cm the top is 200 cm; for a chart of children whose tallest is 110 cm it is 130 cm.
- Grid lines run across every 10 cm, labelled in centimetres down the left side.
- Feet are marked down the right side, one tick for each whole foot. A foot is 30.48 cm, so the ticks do not line up with the centimetre lines, and they are not meant to.
- Each head touches a dashed line in that person's colour, at exactly their height on the grid. That line is the measurement; the figure is just there to make the picture readable.
The figures are simple outlines, like the ones on a signboard, in four shapes: man, woman, boy and girl. A child's head is a larger share of its height than an adult's — the usual proportion charts give about a quarter at birth and a fifth at two years old, against seven to eight heads for an adult — so the boy and girl figures have bigger heads to read as children. Their widths are not to scale: a broad person and a slim person of the same height look the same.
How tall is tall?
A single height means more next to an average. Our World in Data gives the global average for adults born in 1996 as 171 cm for men and 159 cm for women — a gap of 12 cm. Averages differ a great deal between countries and have changed over generations, so the global figure is a rough reference rather than a target.
Against those averages, Rahul at 175 cm is 4 cm above the average man, and Priya at 160 cm is 1 cm above the average woman. You can add a person called "Average man" at 171 cm and "Average woman" at 159 cm to any chart to see where everyone else sits.
At the extreme, the tallest man in medical history for whom there is firm evidence is Robert Wadlow of the United States, last measured at 272 cm — 8 feet 11.1 inches — in June 1940. The tool accepts heights from 30 cm to 275 cm, which covers everyone from a toddler to him; with Wadlow on the chart its top rises to 320 cm.
Measuring a height properly
A comparison is only as good as the heights that go into it, and heights quoted from memory are often a centimetre or two out. To measure at home:
- Take off shoes and anything on top of the head.
- Stand on a hard floor with your back to a wall, heels together and touching the wall.
- Look straight ahead, not up or down.
- Have someone lay a flat book or ruler on top of your head, square against the wall, and mark where its underside meets the wall.
- Measure from the floor to the mark with a tape.
People are slightly taller in the morning than in the evening, because the discs between the bones of the spine are squeezed a little during the day. If you are comparing two people, measure them at about the same time.
Using the tool
- Add up to six people. Each has a name, a figure, a height and a colour. New people start with different heights and figures so they are easy to tell apart.
- Pick the units once for everyone. The box under each height shows the other unit, so you can type in feet and inches and still see centimetres.
- Choose the order. As added, shortest first or tallest first. A line-up from shortest to tallest is the usual way to show a family or a class.
- Download the chart as a PNG picture with every name and height on it, ready to send or post. It is made on your device; nothing you type is uploaded.
If you want to compare two people in other ways, the Age Difference Calculator works out the gap between two birthdays, and the BMI Calculator puts a height and weight together.