How to read an imperial tape measure
What each line means
Each inch is halved, halved again and again, down to sixteenths.
| Line | Marks |
|---|---|
| Longest, with a number | Whole inches |
| Second longest | 1/2, exactly mid-inch |
| Third longest | 1/4 and 3/4 |
| Fourth longest | 1/8, 3/8, 5/8 and 7/8 |
| Shortest | 1/16, 3/16, 5/16 and every gap left |
Some tapes also show 32nds on the first few inches, with even shorter lines.
Reading a measurement in four steps
- Find the last whole inch before the end of the object.
- Look at the length of the line at the end and match it to the table above.
- Count sixteenths from the whole inch if unsure, then reduce the fraction. The chart below lists every one.
- Reading = whole inches + fraction.
Feet and inches
After 12 inches, many tapes mark each foot: "1F", a highlighted box, or the foot number printed with the inch number, such as 1′2″ beside the 14 (′ is feet, ″ is inches). To convert, divide the inches by 12: the result is feet, the remainder is inches, and any fraction stays as it is. With no whole inches left over, write a 0: 1 ft 0 3/8 in.
Worked examples
| Reading | How to get it |
|---|---|
| 5 3/8 in | The end is past the 5 and the 1/4-inch line, short of the 1/2-inch line. Count on from the 1/4 line (4/16): 5/16, 6/16. Six sixteenths is 3/8. |
| 2 11/16 in | A shortest line, one step before the 3/4 line. 3/4 is 12/16, so one step back is 11/16. |
| 2 ft 7 1/4 in | The 1/4-inch line just after the 31 reads 31 1/4 in. 31 divided by 12 is 2, with 7 left over. |
The red boxes and black diamonds
Most tapes show a red or highlighted number every 16 inches (16, 32, 48): 16 in is the standard on-centre spacing for wall studs in the US. Most also have small black diamonds every 19.2 inches (just over 19 3/16) for joist and truss layout, because 19.2 in divides 8 ft (96 in) into 5 equal spaces. For an ordinary length, ignore both.
The loose hook and the case
The hook slides by about its own thickness, on purpose. Hooked over an edge, it pulls out so the reading starts at the edge; pushed against a wall, it moves in by the same amount. Both readings are right, so don't bend the hook or tighten the rivets.
For an inside measurement, such as a window opening, press the back of the case into one side, read where the tape enters the case, and add the case length. Many cases print it, for example "add 3 in".
Common mistakes
- Counting the inch line as one. Start counting at the first line after it, or every reading comes out 1/16 too big.
- Letting the tape sag. A sagging tape reads long, so keep it straight and tight over long distances.
Tape measure fractions chart
| Mark | Reduced fraction | Decimal (in) | mm |
|---|---|---|---|
| 1/16 | 1/16 | 0.0625 | 1.59 |
| 2/16 | 1/8 | 0.125 | 3.18 |
| 3/16 | 3/16 | 0.1875 | 4.76 |
| 4/16 | 1/4 | 0.25 | 6.35 |
| 5/16 | 5/16 | 0.3125 | 7.94 |
| 6/16 | 3/8 | 0.375 | 9.53 |
| 7/16 | 7/16 | 0.4375 | 11.11 |
| 8/16 | 1/2 | 0.5 | 12.70 |
| 9/16 | 9/16 | 0.5625 | 14.29 |
| 10/16 | 5/8 | 0.625 | 15.88 |
| 11/16 | 11/16 | 0.6875 | 17.46 |
| 12/16 | 3/4 | 0.75 | 19.05 |
| 13/16 | 13/16 | 0.8125 | 20.64 |
| 14/16 | 7/8 | 0.875 | 22.23 |
| 15/16 | 15/16 | 0.9375 | 23.81 |
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How to read a metric tape measure
Metric tapes have no fractions to reduce. Switch the interactive tape above to Metric to try the first two examples below.
What each line means
- Longest line, with a number: a whole centimetre (cm).
- Medium line, halfway between two numbers: 5 millimetres.
- Shortest lines: single millimetres (mm). A centimetre is 10 millimetres, so 8 short lines plus the 5 mm line sit between two numbers.
Many tapes highlight every 10 cm, and some show each metre as "1M", "2M" or with a coloured background. Some add a second scale in millimetres.
Reading a metric measurement in three steps
- Find the last numbered centimetre before the end of the object.
- Count the millimetre marks after it.
- Reading = centimetres + millimetres, e.g. 23 cm + 7 mm = 23.7 cm = 237 mm.
Worked examples
| Reading | How to get it |
|---|---|
| 9.2 cm | The end is just past the 9, two short lines after it: 2 millimetres. |
| 14.7 cm | Past the 14 and past the medium line. Count on from that line: 6, 7. |
| 1.36 m | On a long tape, the end lands 36 cm past the 1 m mark: 136 cm in all. |
Centimetres, millimetres and metres
All three are correct; the choice depends on who reads the number. Everyday measurements and schoolwork use centimetres (72.5 cm). Builders, joiners and engineers in most metric countries use millimetres only (725 mm), because a whole number leaves no decimal point to misread. Room sizes and long runs are given in metres (3.2 m). To convert, move the decimal point: one place between centimetres and millimetres, two between metres and centimetres.
The most common metric mistake
Writing 92 cm when you mean 92 mm (9.2 cm) makes a part ten times too big. Always write the unit.
Tapes with inches and centimetres
Dual-scale tapes have inches along one edge and centimetres along the other. Both scales start at the hook, but their numbers rarely line up after that, because 1 inch is exactly 2.54 cm. Divide centimetres by 2.54 for inches, or multiply inches by 2.54 for centimetres. The inch numbers are further apart, so check which edge you're reading before you start, and stay on it for the whole measurement.
Metric to inches quick reference
| Metric | Inches | Nearest 1/16 mark |
|---|---|---|
| 1 mm | 0.039 | 1/16 in (1 mm is nearer 1/32) |
| 5 mm | 0.197 | 3/16 in |
| 1 cm | 0.394 | 3/8 in |
| 5 cm | 1.969 | 1 15/16 in |
| 10 cm | 3.937 | 3 15/16 in |
| 30.48 cm | 12 | exactly 1 ft |
| 50 cm | 19.685 | 1 ft 7 11/16 in |
| 1 m | 39.37 | 3 ft 3 3/8 in |
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Frequently asked questions
What if the end falls between two marks?
Read the nearest mark. Most jobs need nothing finer than 1/16 of an inch or 1 millimetre; for closer work, use a steel rule or callipers.
What does "burning an inch" mean?
Measuring from the 1-inch mark instead of the hook, then taking 1 inch off the reading. Carpenters do it when the hook is damaged or there's nothing to hook onto. On a metric tape, use the 10 cm mark the same way.