How to Measure Your Back Length for Shirts, Coats, and Dresses
Back length is the silent measurement that decides whether a dress's waist seam lands at your waist or below it, and whether a coat's shaped back actually shapes anything. Here's how to take it in two minutes.
You ordered a fit-and-flare dress in your usual size. The bust fit. The hips fit. But the waist seam — the part that's supposed to sit at your natural waist — landed somewhere around your ribs, making the dress look short-waisted and the skirt look like it started halfway up your torso.
The width measurements were right. The vertical measurement was wrong. That's back length: the distance from the base of your neck to your natural waist. Most online shoppers never take it because most brands don't ask for it. But on any garment with a shaped torso (waist seam, dart, fitted blazer back), it's the measurement that decides whether the design lands where the designer intended.
What Back Length Is (and Isn't)
Definition
Things back length is not:
Step-by-Step: Measure Your Back Length
- Stand naturally. Don't slouch, don't arch. Feet about hip-width apart. Wear thin clothing or just underwear.
- Find C7. Tilt your head forward until your chin touches your chest. Run your fingers down the back of your neck — the most prominent vertebra you can feel is C7. That's your top reference point.
- Find your natural waist. Stand straight and lean to one side. The crease that forms on your opposite side is the narrowest point of your torso — your natural waist. It's usually about 1 inch above your belly button.
- Place the tape at C7. Hold the start of the soft measuring tape against C7 with one hand, or have a partner hold it.
- Drop the tape down your spine. Let it hang vertically along the spine. Don't curve it around your body — back length runs along the spine itself, not over the shoulder blades.
- Read at the natural waist. The number where the tape crosses your natural waist is your back length.
Quick check
Typical Back Length by Height and Build
| Group | Typical back length |
|---|---|
| Women's petite (5'4" and under) | 14–16" |
| Women's regular (5'5"–5'8") | 16–17" |
| Women's tall (5'9"+) | 17–19" |
| Men's short (5'7" and under) | 16–17.5" |
| Men's regular (5'8"–6'0") | 18–19" |
| Men's tall (6'1"+) | 19–21" |
Back length scales with height, but not linearly. A long-torso 5'5" woman can have the same back length as an average 5'8" woman. That's why the measurement matters even when you "know" your size — height alone doesn't determine where waist seams land.
When Back Length Matters Most
Fit-and-flare dresses
Tailored blazers and suit jackets
Trench coats and structured outerwear
Wedding gowns and formalwear
Bodysuits, leotards, swimsuits
Common Mistakes
Measuring with the tape over the shoulder blades
Back length runs along the spine — flat against your back. If the tape arches outward over your shoulder blades, you'll add 0.5–1 inch to the measurement.
Starting at the hairline instead of C7
C7 is below the hairline, at the base of the neck. Starting from the hairline adds 1+ inch and makes you appear longer-torso'd than you are.
Reading at the belly button instead of natural waist
The belly button is below the natural waist for most adults — sometimes by an inch or more. Reading at the belly button gives you a number that's too long.
Measuring while slouching or arching
Stand the way you actually stand. Slouching shortens; arching extends. Both make the number wrong for the position you'll wear the garment in.
Using Back Length on Size Charts
Most US mass-market brands don't list back length. Brands that do (Talbots, J.Crew Petite, Boden, Eileen Fisher, most made-to-measure programs) use it to confirm whether you fit petite, regular, or tall cuts:
For more on petite/tall sizing logic see petite vs tall sizing explained.
FAQs
What is back length?
Back length is the distance from the bony C7 vertebra at the base of your neck down your spine to your natural waist.
Why does back length matter?
If your back length differs from the brand's standard, dresses' waist seams won't sit at your natural waist, and shaped jackets won't suppress at the right point.
What is a typical back length?
Average women's back length is 16–17 inches. Petite runs 14–16 inches. Tall runs 17–19 inches. Men's average is 18–19 inches.
Should I measure back length over clothes?
Wear thin clothing or measure in underwear. Bulky clothing adds inches.
Can I measure my own back length?
It's easier with help, but yes — hold the tape at C7 and use a mirror to read at your natural waist.
Is back length the same as torso length?
No. Back length is C7 to natural waist. Torso length is C7 to the crotch or hip.
Save Your Back Length Once
Back length doesn't change much in adulthood (unlike weight-driven measurements). Take it once, save it with your bust/waist/hip numbers, and you'll have it ready next time a dress size chart asks. Read our bust guide, waist guide, and hip guide for the rest of the core set.
Selling structured dresses or coats on Shopify?
When customers can't tell whether to size up for length or pick a tall, they buy two and return one. Tailor Size Guide adds back length to your size chart so customers compare against their own number.