Reading a tape measure accurately is an essential skill for many projects, from hanging a picture at the correct height to building your own house. Yet reading a tape measure can initially seem complicated. When the blade is stretched out, a tape measure at first looks like jumble of numbers, marks, diamonds, and other confusing symbols. But once you break it down into a few basics, a tape measure is actually very easy to use. Reading a tape measure requires just a bit of background in basic fractions, as well as an understanding of how to interpret the marks on today's tape measures.
Tape measures can be more hazardous to the operator than they may seem at first. Do not let a spring-operated tape roll back into place at full force, as you can badly cut your finger and damage the tape. Instead, reel the blade in slowly. If the tape measure blade becomes crimped or cracked, it is best to replace the tool.
With expensive tape measures, it may be possible to buy a replacement blade when the old blade becomes damaged or no longer extends and retracts smoothly. Make sure to buy a replacement authorized by the manufacturer for your tape measure model.
Before You Begin
Measurement marks on a tape measure are the straight lines that run perpendicular to the edge of the blade. Some marks are black and some are red. Most tape measures sold in the U.S. use imperial units of measurements, marked in inches and fractions of inches. But there are also tape measures marked with metric units of measure, and many modern tape measures are dual-purpose, with inch units marked along one edge of the blade and metric units (centimeters and millimeters) along the other edge.
In the U.S., however, building materials are usually sold in imperial unit sizes, and construction standards require tools that measure in inches, feet, and yards. Most tape measures will accurately measure down to increments of 1/16 inch, and some have 1/32-inch markings.
Reading a tape measure is a matter of interpreting the lengths of the perpendicular marks on the blade and determining if your measurement is aligning with a 1-inch, a 1/2-inch, a 1/4-inch, a 1/16-inch, or a 1/32-inch markings. Each of these increments is designated with lines that are progressively shorter as the unit of measurement gets smaller. As the length of the marks progressively shortens, the unit of measurement shortens, as well.
Tape measures come in many forms and lengths. Most use slightly curved metal blades that are coiled up inside a metal casing, with an inner spring that helps retract the blade, as well as a locking lever that holds the blade in an extended position. This type of tape measure is available in a variety of lengths, from 8 feet to 40 feet. Blade width can vary from 1/2 inch up to about 1 1/4 inch. Wider blades will be more rigid when the blade is extended from the casing. Longer tape measures up to 100 feet are usually reel-style devices that use narrower, more flexible blades, and which must be reeled in by hand for retraction.
For general-purpose use, most homeowners find a 16-foot or 25-foot tape measure with a 1-inch or 1 1/4-inch blade to be sufficient. But having two or three tape measures of different sizes in your toolbox is a good idea.
Watch Now: How to Read a Tape Measure
Equipment / Tools
- Tape measure
Find the Foot Marks
Virtually all tape measures will label foot-long increments on the blade. These marks will usually be abbreviated as "x ft," often accompanied by an arrow, or highlighted in red.
Find the Inch Marks
The next increments of measure on a tape measure blade are the inch marks, which will be identified by the longest lines and usually labeled with a single numeral—1, 2, 3, etc. Inch mark numbering usually continues along the entire length of the blade. At 8 feet, for example, you will see both a "8 ft." and a "96" inch designation.
- On some tape measures, the inch markings repeat 1- to 12-inch increments on one side of the blade, with running inch increments on the other side (as shown here).
- On duel purpose tape measures, the numerals on the opposite side of the blade indicate centimeters.
Find the 1/2-inch Marks
The next shortest line, located exactly half way between the inch marks, delineates the half-inch increments. These, and all the subsequent units, will not be identified by numerals.
Find the 1/4-, 1/8-, 1/16-, and 1/32-Inch Marks
From this point on, each previous unit is divided in half by progressively shorter lines, indicating 1/4-, 1/8-, and 1/16-inch increments. These do not have numerical labels, and it takes some practice to recognize which increment you are reading on the tape.
Some tape measures also add 1/32-inch increments, though many people have trouble reading measurements this precise. Fine woodworkers, however, will make use of such precision.
Find the Stud Markings
For the benefit of framing carpenters who do repetitive work, most tape measures also have convenient markings at 16-inch and 19.2-inch increments, usually designated by a number highlighted in red, or by a small diamond marking on the blade. These increments correspond to the common intervals for the studs, joists, and rafters that are used to create the basic structural framework for walls, floors, and roofs. You will rarely use these markings unless you happen to be building a shed or playhouse, or constructing partition walls during major remodeling projects.
These stud designations are intended to indicate the "on-center" position of framing members.
Examine the Catch Hook
Now turn your attention to the tip of the tape measure blade. You may notice that the hook riveted to the end of the blade has a slight amount of looseness that allows it to slide back and forth on the blade by a small degree. This is not a design flaw. This movement allows the tip of the tape measure to either be pressed against a workpiece, or hooked over it. For example, when measuring the inner dimensions of a room from baseboard to baseboard, the tip of the tape measure is pressed tight against the wall, so that the catch hook slides slightly inward as you measure. If you are measuring the outside dimension of a door, on the other hand, the proper procedure is to hook the top over one edge of the door, which will cause it to slide slightly outward on the blade.
In theory, this small amount of looseness makes for a more accurate tape measure that can work equally well making interior or exterior measurements.