How to read a tape measure to a sixteenth of an inch

Reading an imperial tape measure to a sixteenth of an inch is basic tool knowledge for an elevator apprenticeship applicant, and it is used every day on the job. It takes about twenty minutes to learn and a little practice to make automatic.

Read by mark length, not by counting

The trick is that the marks on an imperial tape are not all the same length, and the length tells you what the mark is.

• Longest, with a number — a whole inch.
• Next longest, halfway between the inches — a half inch.
• Next — the quarters, at one quarter and three quarters.
• Next — the eighths.
• Shortest — the sixteenths.

Once you read by length, you do not count sixteen little marks every time. You see the nearest long mark, then count the short ones from there. Three marks past the half is 8/16 plus 3/16, which is 11/16.

Reducing the fraction

Measurements are normally written in lowest terms, so 8/16 is written as a half and 6/16 as three eighths. The rule is to halve top and bottom while both stay whole numbers.

• 2/16 = 1/8
• 4/16 = 1/4
• 6/16 = 3/8
• 8/16 = 1/2
• 10/16 = 5/8
• 12/16 = 3/4
• 14/16 = 7/8

Odd numbers of sixteenths do not reduce at all, so 5/16, 7/16, 9/16, 11/16, 13/16 and 15/16 stay as they are. That is a useful shortcut: if the number on top is odd, you are already finished.

Working in sixteenths

The fastest way to add, subtract or compare imperial measurements is to convert everything to sixteenths first. Is 5/8 bigger than 9/16? In sixteenths that is 10/16 against 9/16, so yes. Adding 3/8 and 7/16 becomes 6/16 plus 7/16, which is 13/16.

Multiply the top by whatever turns the bottom into 16. Eighths double, quarters multiply by four, halves by eight.

The mistakes that cost marks

• Reading from the wrong inch. Check the whole number before you worry about the fraction.
• Miscounting by one mark. Always count from the nearest long mark, never from the inch line.
• Forgetting to reduce. 6/16 is correct arithmetic, but multiple-choice options are usually written as 3/8.
• Confusing eighths with sixteenths. If you are not sure which you are looking at, find the half-inch mark and work out from there.

Practice on an actual tape

Reading fractions off a list is not the same skill as reading them off a tape. Our tools and measuring practice draws the tape with an arrow on it, so you practice reading the instrument rather than a list of fractions.