Why the details matter
Tape measures look alike, but small differences affect how far you can measure, how easily you can work alone, and how often you make a reading mistake. Choosing well usually means thinking about the kind of measuring you do most: rooms and long boards, cabinet and furniture parts, or quick household checks.
Length
Common lengths are 12, 16, 25 and 30 feet, with metric versions in meters. For most home and shop use, a 16 or 25 foot tape is a practical middle. A 12 foot tape is small and light, good for a pocket or a drawer. A 25 foot tape handles most rooms, framing and lumber lengths. Longer tapes are heavier and bulkier, and the blade tends to need more care to keep straight.
If you work on large spaces such as long walls or exteriors, a longer tape or a laser distance measurer may suit better. A single long tape is more accurate than combining several short measurements, because each added reading adds a possible error.
Blade width and stand-out
Blade width is typically about 3/4 inch up to 1-1/4 inches. A narrower blade is easier to carry and tends to be found on small tapes. A wider blade is stiffer and stays straight farther when extended horizontally.
That distance is called stand-out: how far the blade extends without support before it folds or bends. It matters when you measure alone across a gap, up a wall or to a ceiling, because a tape that stands out well lets you hold the end in place without help. Stand-out depends on blade width, curvature and material. Manufacturers often state it, but the figure varies by test, so try the tape if you can. A wider blade also takes a greater bend to roll up and may be harder to fit in small cases.
A coated or lacquered blade resists wear and keeps the markings readable. A plain blade may show scratches sooner. Some blades are matte to reduce glare, and others use high-contrast colors to read quickly in poor light.
The hook
The metal hook at the end of the blade is designed to move slightly. When you hook it over an edge to take an outside measurement, it pulls out to sit against the edge. When you push it against a surface for an inside measurement, it slides back. The distance it moves is meant to equal the thickness of the hook itself, so both readings stay accurate.
This is why a loose hook is not necessarily a defect. A hook that is bent, loose to the point of rattling excessively or caught on dirt will give errors, though. Check it by measuring a known length from the hook and again from the 1 inch mark. If the two disagree by a noticeable amount, the hook may be damaged. Do not use pliers to straighten it unless you re-check it against a reliable rule. Some people prefer to measure from the 1 inch mark for critical work and subtract it, which removes any dependence on the hook.
Hook design varies. Wider hooks hold an edge better. Some have a notch or a slot for a nail head so you can hang the tape on a screw to measure alone. A hook with a magnetic tip can hold on a metal surface, which helps when measuring steel stock or inside ducts.
Markings
Imperial tapes usually mark inches divided down to 1/16 inch, with some showing 1/32 inch on part of the blade. Metric tapes show millimeters and centimeters. Dual-scale tapes carry both on opposite edges, which is helpful but busier to read.
Many tapes include special marks used in building. A mark every 16 inches is common because wall studs are often spaced 16 inches on center. Black diamonds at 19.2 inches indicate truss spacing, since 19.2 inches fits five spaces into 8 feet. Such marks are conveniences, and local practice varies, so confirm the spacing for your project instead of assuming.
Some tapes print fractions on the blade, which saves arithmetic if you work in feet and inches, and others print totals in inches. Choose a layout you can read at a glance. Numbers that run in both directions let you read from either side of an opening. High-contrast print on a light blade is easier on the eyes in a dim space.
Reading accuracy
A tape is only as accurate as the person reading it. Look straight down at the mark rather than from an angle, since parallax can shift where the line seems to fall. Keep the blade flat and straight. A sagging tape across a long span reads a little longer than it should, so support it if you can. Check that the hook is seated against the edge before you read.
Choose a consistent method, for example always reading to the nearest 1/16 inch and noting which side of the line your pencil mark sits on. Mark with a fine pencil line or a V-shaped tick that points to the exact spot, not a thick dash. For anything critical, measure twice, and use the same tape throughout a job, since two tapes can disagree by a small amount. To check yours, compare it against a steel rule now and then. Many tapes also print the case width on the case, which you add when pressing the case into a corner for an inside measurement. For work that needs repeatable sizes, such as many identical parts, story sticks can save you from reading and re-reading the tape. Rooms are a good example of why consistency counts, since squaring a room depends on comparing measurements taken the same way. Finer work, where a sixteenth matters, belongs with tools made for precision measuring, such as a steel rule or calipers, and routine accuracy checks keep a tape honest.
Case and lock
Case size and grip affect comfort. A rubber over-mold helps with drops and grip, and a belt clip helps you keep the tape handy. A blade lock holds the extended blade in place, which is especially valuable for reading from a distance. A retraction brake slows the blade and reduces whipping. Always keep your hands away from the blade edge when retracting, since it can cut skin, and do not let it snap back at full speed against the case, which damages the hook and rivets.
Care
Keep the blade clean and dry, wipe off sawdust and moisture, and avoid stepping on or kinking it. Do not let the blade stay extended in wet or dusty conditions. A crease permanently weakens the blade. When the markings wear off, the hook is bent beyond repair or the blade shows kinks, replacing the tape is cheaper than a wasted piece of lumber.