To measure your torso length, you need a flexible tape measure and two bony landmarks on your spine: the C7 vertebra at the base of your neck and the top of your hip bones (the iliac crest) at the back. The distance between these two points is your torso length, and it typically falls between 15 and 22 inches for most adults. This measurement matters most for backpack fitting, but it’s also useful for bike sizing, clothing, and ergonomic setups.
Finding Your Two Landmark Points
The measurement starts and ends at specific bones you can feel through your skin. Getting these right is the whole game.
C7 vertebra (top landmark): This is the large, bony bump at the base of your neck where it meets your shoulders. To find it, tilt your chin down toward your chest. Run your fingers along the back of your neck and feel for the most prominent bone that sticks out. That’s C7. A quick confirmation trick: the vertebra just above it (C6) will shift forward when you extend your neck back, but C7 stays put.
Iliac crest (bottom landmark): Place your hands on your hips with your fingers pointing forward and your thumbs wrapping around to your back. Your thumbs should naturally rest near the top of your hip bones. The point where an imaginary line between your two thumbs crosses your spine is your bottom landmark. Some guides refer to this as the “iliac crest line,” and it sits roughly at the level of the beltline or just above it.
Step-by-Step Measuring Process
You’ll get the most accurate result with a helper, though it’s possible to do alone with some patience.
- Stand up straight with your normal posture. Don’t exaggerate your height or slouch.
- Tilt your head forward so your helper can locate C7. Have them place a small piece of tape or a pen mark on the skin right over that bone.
- Find the iliac crest using the thumbs-on-hips method described above. Mark where that line crosses your spine.
- Run a flexible tape measure along the curve of your spine from C7 down to the iliac crest mark. Don’t hold the tape straight in the air behind you. It should follow the natural S-curve of your back, since that’s the surface a backpack frame or chair actually contacts.
- Read the measurement in inches. Most sizing charts use inches, though some European brands use centimeters.
If you’re measuring alone, use a mirror and a flexible ruler or sewing tape. It helps to stick small pieces of painter’s tape on each landmark first so you have visible targets.
Torso Length for Backpack Sizing
This is by far the most common reason people measure their torso. Hiking and travel backpacks transfer weight to your hips through a suspension system, and that system only works if the pack length matches your spine length. A pack that’s too long will sit the hipbelt on your thighs instead of your iliac crest, and one that’s too short will pull the shoulder straps down painfully.
Osprey, Gregory, and most major pack brands use the same C7-to-iliac-crest measurement. General sizing ranges look like this:
- Extra small: under 16 inches
- Small: 16 to 18 inches
- Medium: 18 to 20 inches
- Large: 20 to 22 inches
These ranges vary by brand and model, so always check the specific pack’s size chart. Some packs come with adjustable suspension that covers a two- or three-inch range, which gives you more flexibility if you’re between sizes.
Torso Measurement for Bike Fitting
Bike fit uses your torso length differently than backpack sizing. On a bicycle, what matters is how far you’re reaching forward to the handlebars, which depends on both your torso and arm length combined. One common starting formula for mountain bikes estimates your ideal frame reach as your torso plus arm length, divided by two, plus about 4 centimeters.
That said, reach preference is highly individual. Two riders with the same torso length might prefer very different frame sizes depending on flexibility, riding style, and how upright they want to sit. Torso length gives you a starting point for narrowing down frame sizes, but a professional bike fit or demo rides will tell you more than any formula.
Torso Proportions and Why They Vary
People of the same overall height can have surprisingly different torso lengths. Someone who is 5’10” might have a torso anywhere from 17 to 21 inches depending on their proportions. This is why height alone is a poor guide for gear sizing.
The ratio of sitting height (a proxy for torso length) to standing height changes throughout life. In infancy, the torso accounts for roughly two-thirds of total body length. During childhood, the legs grow faster than the spine, and by adolescence, the torso represents closer to 50% of total height. This ratio also varies across populations and between individuals, which is exactly why measuring is more reliable than guessing based on height charts.
Front and Back Torso for Clothing
If you’re measuring for custom clothing or sewing patterns, you’ll need more than one torso number. Tailors typically take a front waist length (from the base of the neck over the shoulder, down the chest to the natural waist) and a back waist length (from C7 down the spine to the waist). These two measurements are rarely equal. Someone with a broader chest or stomach needs more vertical fabric in the front to travel over those curves. Someone with a more stooped posture needs extra length in the back. Treating front and back as identical is one of the most common reasons off-the-rack shirts pull or ride up.
For the back measurement, the technique is the same as the backpack method, just stopping at the natural waist (the narrowest point of your midsection, usually a few inches above the iliac crest) rather than at the hipbone. For the front, start at the highest point of the shoulder near the neck, drape the tape over the fullest part of the chest, and measure down to the waist.
Torso Length for Chair and Desk Ergonomics
Choosing an office chair with proper lumbar support depends partly on how long your torso is. The lumbar curve of the chair needs to align with the inward curve of your lower back, which sits at a different height on every person. If you’re over about 6’2″, standard office chairs often have backrests that are too short to support your upper back and shoulders, and the lumbar pad may sit too low.
A useful related measurement for chair fitting is seat depth: sit with your back flat against a wall and measure the horizontal distance from your lower back to the crease behind your knees. This tells you how deep the seat pan should be. If the seat is too deep, the front edge presses into the backs of your knees. Too shallow, and your thighs lack support. Most people fall between 16 and 20 inches for this measurement.