How to read the lines on a measuring tape

We've all heard the saying "measure twice, cut once," but what if you’re not reading a tape measure correctly in the first place? Learning how to read a tape measure may seem simple, but knowing all the special markings and the metric and imperial tape measure lines could be the difference between a great shelf and another piece of scrap wood. 

So whether you're measuring the square footage of a space or building your very own farmhouse table, we've got the tips for reading your measuring tape measurements the right way.

What Are the Parts of a Tape Measure?

Tape measures come in plastic, metal, and even roll-up cloth measuring tape form. For our purposes, we're talking about a standard construction tape measure—the extendable metal or plastic tape that zips out of the case and zips back in when you release the lock. Let's get to know the tape measure a bit better:

• Case (or housing): The case of a tape measure that houses the tape and controls its extension and withdrawal. Your case may note its length so you can use it while measuring tight spaces.

• Belt loop: Most cases include a clip on one side to pop on your belt or work apron in between measurements.

• Thumb lock: The thumb lock is a small switch just above the tape dispenser to allow the tape to move in either direction.

• Tape (or blade): The tape rolls up inside the case but will extend out to 10, 25, 50 feet, or even longer in some cases. The tape often includes both metric and imperial tape measure lines.

• Hook (or tang): A metal or plastic hook tops the end of the tape for several reasons. It stops the tape from disappearing into the case, latches onto the edge of a surface, and even includes a small hole for temporarily attaching to a surface for more stability. Some hooks will include a serrated edge to mark your measurement if you don't have a pencil handy.

How to Use a Tape Measure

After ensuring that the lock is in the off position, gently pull the hook—aka the tang—out of the case. Now you're ready to measure:

1. If you are measuring an object or area with an edge, brace the hook against the end of the object and pull the tape measure to the proper length. 

2. Click the tape into the locked position to observe and mark the measurement. 

3. Here's the interesting part: The hook on the end of the measuring tape is often slightly loose to account for this measuring process. Since "true zero" sits underneath the hook, the hook will pull away from the tape 1/16 of an inch to account for the extra material. In other words, you can trust that you have an accurate measurement even with that small hook at the end.

4. Mark the measurement with a pencil, preferably pointing to the spot with an arrow instead of just a line.

5. Always cut closer to the larger measurement—you can always sand down the wood later.

Photo: rawpixel.com / Adobe Stock

With the tape measure right where you need it, let's get down to reading the numbered tape measure. Even if you recall these geometry lessons from your school days, it can be helpful to know just how a tape measure tends to break things up.

Keep in mind that every model of tape measure will use different fonts and highlight different important measurement lengths.

Read an Imperial Tape Measure

Most tape measures in the U.S. will include imperial units—feet, inches, and all the divisions of an inch in between. If it is not clearly marked, remember that inches are larger than centimeters so that numbers will be farther apart on the imperial unit side.

Feet

One foot will appear on a tape measure as 1', 1F, 1ft., or simply 12 inches. Some tape measures will highlight each foot marking so they are easier to see when stretching the tape across long distances. 

Inches

One inch will be noted as 1", 1in, or just with the number itself. The numbers for inches will often be the largest on the tape measure and easy to spot from afar. The line for inches may even span the entire height of the tape measure.

Half Inches

The next largest mark on the imperial side of the tape measure is the half-inch mark. Some tape measures will indicate this for the first few inches or throughout the entire thing. You will often see it marked as ½" or with nothing other than the line. 

Quarter Inches

Look in between each half-inch, and you'll find mid-sized markings for quarter inches. There will be two quarter-inch marks between each half-inch mark. Yet again, some measuring tapes will include a ¼" note, while others will simply include the line.

Eighth Inches

Take an even closer look, and you'll find that each quartered inch is split in half by a small eighth-inch marking. The line will be even shorter than the quarter-inch one and may or may not include a ⅛" note. 

Sixteenth Inches

The sixteenth-inch—you guessed it—splits up the eighth-inch sections. These are so small that they rarely get a note, but if they do, it will look like 1/16". 

Read a Metric Tape Measure

Photo: tostphoto / Getty Images

Many countries outside of the U.S. opt out of the imperial inch, foot, and mile system and go for the metric system. Measurements in the metric system use the meter. The meter is 100 centimeters, which breaks down into 10 millimeters. Tape measure lines may also make a special note for the decimeter—or 10 centimeters—so it's easier on the eye when measuring. 

Meters

You will find a large marking, sometimes in red or bolded black, for the meter. The tape may list it as 1m, or as 100cm. 

Decimeters

Some measuring tapes will break meters into decimeters, marked as dm. Every 10 centimeters, a red or black bolded number will indicate that you've reached 10cm. 

Centimeters

Centimeters, or cm, are the primary measuring unit on the metric tape. If your tape has both, the centimeter numbers often fall below the imperial numbers. Centimeters will be marked with numbers, a tall line, or 1cm, 2cm, and so forth.

Millimeters

Millimeter lines break centimeters into 10 sections so you will find nine markings between the two-centimeter lines. Some measuring tapes will include a slightly taller line to mark the halfway point between two centimeters to make it easier to count.

Tips for Using and Reading a Tape Measure

There are some hidden secrets you can lean on when learning how to read a tape measure. Some tape measures highlight important numbers for builders and feature small design perks to make them easier to use.

Read Special Markings

Even if you've used a tape measure for years, you may have missed the hidden markings. For example, here are a few:

• 16-inch markings for common stud spacing

• 19.2-inch markings for common joist spacing

• 19 3/16-inch markings for common truss spacing

Find Your Case Length

If you are measuring in a tight space, do not bend the case away from the measuring surface and press the tape down. You will get a better measurement by extending the case right to the wall and adding the length of the case (usually about 3 inches) to your measurement. The case should include its length on the back.

Draw a Circle

Do you know what else the handy hook is good for? Drawing a perfect circle before cutting. Place the hook on a nail at the center of the circle you intend to draw. Pull the tape out to the proper radius and lock it into place. Place your pencil at the junction of the case and the tape and spin it around for a perfect circle.

Wind It Up Slowly

We all had a bit of not-so-safe fun letting the measuring tape zip back into the case when we were kids. It's not the best idea when working, however. Always feed the tape back into the case slowly when winding up the tape to avoid injury.

Frequently Asked Questions

What do the little lines on the tape measure mean?

The small lines on the tape measure either indicate inches, fractions of an inch, or centimeters and millimeters. On the imperial unit side (aka the inches side), the longest lines indicate inches, followed by the next shortest lines that indicate a half-inch, and then the quarter, eighth, and sixteenth-inch. On the metric side, the lines break down meters, centimeters, and millimeters.

Do you measure from 0 or 1 on a measuring tape?

Measure from zero on a measuring tape by placing the metal hook right up against the edge of what you need to measure. You can also latch the hook onto an open edge—of, say, a table—to accurately measure as well. If you begin at the 1-inch mark, you'll need to subtract an inch from your total.

Why is there a hole at the end of a tape measure?

The hole on the hook—also known as the tang—allows you to secure the end of the tape with a nail or thumbtack when pulling the tape a long distance.

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