Tape measure markings demystified

DEAR TIM: I’m just starting to get into building and remodeling as a do-it-yourselfer. Now that I’m using a tape measure, I’m having some difficulty. Perhaps I should have paid more attention in math class. Can you tell me about the markings on tape measures, what they mean and about all the special markings? Also, every tape measure I have and see in the store seems to be defective. The hook on the end is loose on all the tapes. What other tips do you have about using tape measures? – Craig S., Billings

DEAR CRAIG: I’ve got some sobering news for you. As you delve deeper into building and remodeling, you’re going to really regret not paying more attention in all your math classes, especially geometry. But if you have the passion to build and remodel, you’ll get up on the math learning curve very fast.

In the past few years, I’ve seen more improvements in tape measures than I’d seen in the previous 35! It’s hard to believe you could improve a tape measure, but a few companies have really done an amazing job.

Most tape measures have black lines perpendicular to the edge of the tape measure in between each of the inch markings. These lines are different lengths to help you differentiate between them.

The longest of these black lines indicates the half-inch mark.

The next-longest lines on the edge are the quarter-inch markings. The longer half-inch mark overlaps one of these three markings between each of the primary inch marks. If you count the quarter-inch markings, including the half-inch mark, you’ll count four between each inch mark. Thus, these markings divide 1 inch of length into four equal parts, each one-quarter inch long.

The same is true for the next two smaller markings on the tape measure. The next smaller line below the quarter-inch mark is for one-eighth and the shortest line represents the one-sixteenth inch mark.

Some tape measures along one side of the tape measure have the actual measurement called out by each line. I have a tape measure that has 1/8, 1/4, 3/8, 1/2, 5/8, 3/4 and 7/8 fractions right above each line. You may want to invest in this tool.

Some tape measures have markings that divide each inch into thirty-seconds of an inch. Most tapes that have this only do it for the first few inches on the tool.

As you extend the tape measure, you’ll probably see the numbers 16, 32, 48, 64, 80, 96 and so forth in red. The red indicates 16-inch-on-center spacing. This is a common framing spacing for wall studs, floor joists and common roof rafters. If you decide to space framing at 24-inch centers, the red marks will be at every other foot marking on the tape measure.

Many people wonder about the small black diamond markings or black triangles found at 19 3/8 intervals on the tape measure. These are handy markings if you want to achieve equal spacing for five framing members per every 8 feet. If you decide to use 16-inch on center spacing, you’ll end up with six framing members for every 8 feet. If you space things at 24-inch centers, you’ll have four framing members for each 8 feet. Some carpenters like to have five framing members per every 8 feet so the sheathing over the framing is less spongy and stiffer.

The hook end of your tape measure is supposed to wiggle a little bit. That’s not a defect. The amount of movement should equal the thickness of the hook end of the tape measure. This is done so you get an accurate measurement when you’re trying to determine the exact measurement in between two fixed objects.

When you get the measurement pushing the tape hard in between the objects and then take the tape and pull it across the board, the movement of the hook will produce the correct measurement. If the hook doesn’t move, you’ll discover your cut piece will always be too short.

The top tips for tape measures are simple. Keep them clean and free of debris. When retracting a tape measure slow it down so the hook doesn’t come to an abrupt stop. Check the hook end of the tape measure before working to ensure it’s at a 90-degree angle to the actual metal tape. If you drop the tape and the hook gets bent, you’ll discover you’ll be getting inaccurate cuts if someone else is giving you measurements.