To measure back length, find the bony bump at the base of the neck, then run a soft tape straight down the center of the spine to the natural waist. Keep the tape flat but not tight, stand tall, and read it to the nearest 1/8 inch (about 0.3 cm).
Back length is one of the quieter numbers on a sewing pattern envelope, yet it decides where a waistline, a darted bodice or a fitted jacket actually sits. Sewing patterns call it “back waist length”. Similarly, the international body-measurement standard calls it “back neck point to waist”. All three names describe the same vertical line down the spine.
The idea is simple, but small details change the result. For example, a slouch can add or remove half an inch. Likewise, a waist marker that tilts can do the same. That is why a careful reading uses two clear landmarks, a relaxed upright stance, and a tape that follows the curve of the back instead of cutting across it.
In short: start at the neck bone, end at the natural waist, follow the spine, and measure twice. Then write the number down in both inches and centimeters so you can match any size chart.
These landmarks are not a home-sewing invention. The ISO standard for clothing body measurements, ISO 8559-1, defines a “back neck point to waist” length from the same neck bone. In addition, a pattern-company fitting guide tells sewists to lower the head, find the prominent bone at the base of the neck, and measure from it to the waistline.
Below you will find a converter, a step-by-step method, a size table, a solo technique, and a short section on measuring a dog for a coat.
Convert Your Back Length From Inches to Centimeters
Pattern charts in the US use inches, while most European and Asian charts use centimeters. So enter your reading below. The converter uses the exact definition of 1 inch = 2.54 cm and also shows millimeters and feet.
Recommended Tape Measures for Back Length
A soft tape is the only tool that really matters here. First, choose one with both inch and centimeter scales, because size charts mix units. Next, look for fiberglass or a stiff vinyl that will not stretch over time. Also, a longer tape helps if you later want full back length to the floor, and a narrow tape sits more neatly along the spine.
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- Back length runs from the neck bone (the 7th cervical vertebra) to the natural waist.
- It follows the spine, so the tape lies flat on the body, not in the air.
- Tie a string or elastic around the waist first; it gives you a clear end point.
- Most misses pattern charts list about 15 1/2 to 17 3/4 inches (39.4 to 45.1 cm).
- Read to the nearest 1/8 inch, measure twice, and average close readings.
- A helper gives the best result; a wall-and-tape trick works if you are alone.
- For dogs, coat makers usually measure from the base of the neck to the base of the tail.
What Back Length Means and How It Differs
On a person, back length is a vertical body measurement. It starts at the back neck point, which is the bony bump you feel when you bend your head forward. That bump is the 7th cervical vertebra, often called C7. The measurement then ends at the natural waist, the narrowest part of the torso, where the body bends sideways.
However, people often confuse it with garment measurements and with other body lengths. The old version of this page, for example, said to measure to the hem of the garment. That describes a garment length, not a body measurement. The table below separates the terms you will see on patterns and size charts.
| Term | Where it starts and ends | What it is used for |
|---|---|---|
| Back length (back waist length) | Neck bone (C7) to natural waist, along the spine | Bodice and jacket fit, waistline placement |
| Front waist length | Shoulder at the neck, over the bust, to the waist | Front bodice length, bust room |
| Full back length | Neck bone to the floor or to a chosen hem | Dresses, coats, gowns |
| Garment center back length | Neckline seam to hem on the garment itself | Comparing a finished piece with a chart |
| Across back (back width) | Horizontal, between the arm creases | Shoulder and armhole room |
| Torso length | Usually neck bone to the top of the hip bones | Backpack and harness sizing |
How to Measure Back Length Step by Step
This method takes about two minutes with a helper. Wear a thin, close-fitting top or measure over bare skin, because a bulky collar or a thick sweater adds length.
- Mark the waist. Tie a piece of string or narrow elastic around your middle and let it settle at the narrowest point.
- Stand naturally. Face forward with feet hip-width apart, arms relaxed, and eyes level. Do not tuck the chin or arch the back.
- Find the neck bone. Bend your head forward briefly so your helper can feel the most prominent bump, then lift your head back to level.
- Place the zero end. Your helper holds the zero end of a soft tape on the center of that bone.
- Follow the spine. Next, they let the tape run straight down the center of the back, resting on the body, until it reaches the bottom edge of the string.
- Read the tape. Read it to the nearest 1/8 inch or 0.5 cm, while you breathe normally.
- Repeat once. Finally, take a second reading. If the two differ by more than 1/4 inch (about 0.6 cm), check the landmarks and measure a third time.
Then convert the result with the tool above if your pattern uses metric sizes. For the matching width measurement, see our guide on how to measure your waist.
Finding the Neck Bone and the Natural Waist
Most errors come from the two end points, not from the tape. Here is how to find each one reliably.
The neck bone. When you bend your head forward, one bump at the base of the neck usually stands out more than the others. That is C7. Some people have two bumps of similar size. In that case, ask your helper to keep a finger on the upper bump while you turn your head slowly. The C7 bone barely moves, while the bone above it shifts a little.
The natural waist. Bend to one side; the crease that forms is close to the natural waist. The string trick works because a loose cord slides to the narrowest point on its own. Also, it gives your helper a clear line to read against, so you do not need to guess.
Typical Back Length by Pattern Size
A size chart gives you a quick sanity check. For example, the pattern-company fitting guide cited above lists the following back waist lengths for misses patterns. They assume a figure about 5 ft 5 in to 5 ft 6 in tall without shoes. We converted the inches with the exact 2.54 factor.
| Misses size | Back waist length (in) | Back waist length (cm) |
|---|---|---|
| 4 and 6 | 15 1/2 | 39.4 |
| 8 | 15 3/4 | 40.0 |
| 10 | 16 | 40.6 |
| 12 | 16 1/4 | 41.3 |
| 14 | 16 1/2 | 41.9 |
| 16 | 16 3/4 | 42.5 |
| 18 | 17 | 43.2 |
| 20 | 17 1/4 | 43.8 |
| 22 | 17 3/8 | 44.1 |
| 24 | 17 1/2 | 44.5 |
| 26 | 17 3/4 | 45.1 |
Your own number can easily differ from the chart by half an inch or more. That is normal, because torso length varies with height and posture, not only with dress size. So if your back length is shorter than the chart, shorten the pattern at the “lengthen or shorten here” line above the waist. Likewise, if it is longer, lengthen it at the same line. For sleeves, the same habits apply; see how to measure sleeve length.
How to Measure Your Own Back Length Without Help
A helper is best, because you cannot see your back. Still, you can get a usable number on your own with this wall method:
- Tie the waist string as before and stand with your back against a door frame or wall.
- Press a sticky note or a ruler flat against the wall at the level of your neck bone; feel for the bone with your fingers to set the height.
- Mark the wall at the bottom of the waist string in the same way, then step away.
- Measure the distance between the two marks with a rigid tape.
However, this gives a straight-line distance, while the real measurement follows the curve of your spine. As a result, the wall reading often runs a little short, especially if you have a rounded upper back. Another option is to hang a soft tape over one shoulder from the neck bone and check the waist reading in a mirror, or with a phone photo.
Back Length for Dog Coats and Harnesses
The old version of this page mixed people and animals in one method. They need different landmarks, so here is the dog version on its own.
Most dog coat makers measure back length from the base of the neck, where the collar sits, to the base of the tail. First, have your dog stand square on all four feet with the head level. Next, lay a soft tape along the spine without pressing into the coat. Then read it at the point where the tail meets the body. Because brands differ, always check the maker’s own size chart before you order.
A chest girth reading usually goes with it. For that, see our guide to girth measurements.
Do and Don’t
Do
- Use a soft tape with inch and centimeter scales.
- Mark the waist with string or elastic first.
- Keep the tape resting on the spine, not floating.
- Stand the way you normally stand.
- Write down both readings and the date.
Don’t
- Start at the collar seam of your shirt.
- Pull the tape so tight it dents the skin.
- Average readings taken at different points on the back.
- Suck in, slouch or tuck your chin.
- Measure over a hoodie or a thick sweater.
Honest Limits of a Tape Measurement
A tape gives a good number, not a perfect one. For one thing, the waist is a soft landmark, so two careful people can place it a little differently. Moreover, posture changes through the day, and a deep breath moves the waist string. A study of 90 women also found that different waist definitions and instruments gave different results, and that many waists were not horizontal. In short, treat a variation of about 1/4 inch (0.6 cm) as normal, and use the same method each time you measure. For sewing, that is close enough, because you will still check the fit on a muslin or a basted test garment.
When to Call a Professional
For special garments, a professional fitting is worth the cost. A tailor or dressmaker can measure you in the shoes and underwear you plan to wear, and can see posture details such as a forward head or a high hip. That matters for wedding dresses, suits and uniforms. Similarly, a bra fitter or an outdoor-store fitter will handle related measurements for bras and backpacks. Our guide on how to measure bra size covers that one.
Back Length FAQs
What is back length?
Back length is the distance from the bony bump at the base of the neck (the 7th cervical vertebra) down the center of the spine to the natural waist. Sewing patterns call it back waist length.
Where do you start measuring back length?
Start at the most prominent bone at the base of the neck. To find it, bend your head forward and feel for the bump that stands out most, then lift your head back to level before you measure.
Where does the measurement end?
It ends at the natural waist, the narrowest part of the torso. Tying a string around your middle shows exactly where that is.
What is an average back length for women?
Misses pattern charts list about 15 1/2 to 17 3/4 inches (39.4 to 45.1 cm), rising with size. Your own number can differ by half an inch or more.
Is back length the same as torso length?
No. Both start at the same neck bone, but torso length for backpacks usually ends at the top of the hip bones, so it is longer.
Can I measure my back length by myself?
Yes, with a wall method. Mark the neck bone height and the waist string height on a wall, then measure between the marks. It may read slightly short, because it ignores the curve of the spine.
Can I use a string instead of a tape measure?
Yes. Lay the string along the spine, pinch it at the waist, then lay it flat against a ruler or a rigid tape to read it.
Should I measure back length over clothes?
Measure over bare skin or a thin, close-fitting top. Thick fabric or a collar adds length and moves the neck landmark.
How precise does back length need to be?
For sewing, the nearest 1/8 inch or 0.5 cm is enough. Readings within about 1/4 inch of each other count as consistent.
How do you measure back length on a dog?
Measure from the base of the neck, where the collar sits, to the base of the tail, with the dog standing square. Then check the coat maker’s own size chart.
Back Length: The Bottom Line
To sum up, a good reading needs just two landmarks: the neck bone and the natural waist. Tie a string at the waist, stand naturally, and let a soft tape follow the spine between them. Then read it to the nearest 1/8 inch and repeat once.
After that, compare your number with the pattern chart and adjust the bodice at the lengthen or shorten line. If you sew for others, also record the date and the method, so later fittings stay consistent.
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