How to Measure Your Back Length for a Backpack

If you’ve ever worn a backpack that didn’t feel quite right—slipping off your shoulders, sitting too high, or digging into your lower back—you’ve experienced what happens when the back length doesn’t match your body. Your back length, also called torso length, is the single most important measurement for choosing or customizing a backpack that fits comfortably and carries weight efficiently.

In this guide, you’ll learn exactly how to measure your back length at home, what tools you need, and how your measurement affects selecting the right pack size.

Why Back Length Matters

Backpacks are engineered around torso length—not your height. Two people of the same height can have very different torso lengths, so relying on height leads to poor fit.

A properly fitted backpack will:

• Distribute weight onto your hips rather than your shoulders

• Keep the center of gravity stable

• Improve comfort over long distances

• Reduce strain on your neck and spine

Custom-fit packs are built around your exact back length, so getting this measurement right is essential.

What You Need

• A soft measuring tape (or a string + a ruler)

• A friend (highly recommended)

• A mirror (if measuring solo)

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Step 1: Locate Your C7 Vertebra

Your C7 vertebra is the bony bump at the base of your neck—it becomes prominent when you tilt your head forward. This is your upper reference point.

Step 2: Find the Top of Your Hip Bones (Iliac Crest)

Place your hands on your hips and feel for the top ridge of your pelvic bones.

Draw an imaginary horizontal line from the top of one hip across to the other. Where this line crosses your spine is your lower reference point.

Step 3: Measure Between the Two Points

Using a soft tape, measure the distance from your C7 vertebra straight down to the spot where the iliac crest line meets your spine. This measurement is your torso/back length.

Back Length Ranges

While everyone is different, typical ranges look like this:

Size	Torso Length
Short	39–44 cm
Regular	44–49 cm
Long	49-54 cm

Custom backpacks will use your exact number and premade packs are made to the above sizes.

Tips for an Accurate Measurement

• Stand naturally—don’t stretch upright or slouch.

• Ask a friend to help for best precision.

• If measuring solo, use a mirror and mark points lightly with tape first.

• Repeat twice to confirm consistency.

  
  

How This Measurement Affects Backpack Fit

Backpacks are designed so the hip belt sits centered on your iliac crest while the shoulder yoke aligns at or just below the C7 vertebra.A correct torso length ensures:

• The hip belt carries 60–80% of pack weight

• Shoulder straps contour naturally

• The load lifters are angled correctly

• The pack’s frame matches your spine

If your torso length is off—even by an inch—the whole fit can shift.

Conclusion

Measuring your back length is quick, simple, and incredibly important for getting a custom-fit backpack that feels balanced, stable, and comfortable. With the diagrams and steps above, you can confidently take your torso measurement at home and ensure your next pack fits exactly as it should.