Harness Sizing Is Two Numbers, and They Can Disagree
Harness sizing looks like a single question and is really two, which is why the answer sometimes comes back contradictory.
Height picks the size, weight checks it
Manufacturers band harnesses by pilot height, because that is what determines whether the seat, back and leg geometry fit you. Each size then has a certified all-up weight range. The harness size calculator does both:
| Pilot | Size | Height band | Weight range | Verdict |
|---|---|---|---|---|
| 175 cm, 90 kg | M | 172–184 cm | 75–105 kg | within range |
| 160 cm, 70 kg | S | 160–172 cm | 55–85 kg | within range |
| 190 cm, 110 kg | L | 184–196 cm | 95–130 kg | within range |
| 175 cm, 70 kg | M | 172–184 cm | 75–105 kg | below range |
| 168 cm, 105 kg | S | 160–172 cm | 55–85 kg | above range |
The last two rows are the interesting ones. A tall, light pilot and a short, heavy one both get a size from their height that their weight does not support — and that is not an error in the tool, it is the actual situation. Bodies do not come in manufacturer proportions.
What to do when they disagree
The tool flags it rather than resolving it, deliberately, because the resolution is not arithmetic.
Going a size down for a light pilot may fit the weight range and be too short in the back or too narrow in the seat. Going up for a heavy pilot may fit the weight and leave the geometry loose, which affects how the harness behaves in flight and how you sit under it.
This is where a manufacturer's own chart matters, because the general bands here are industry-typical rather than anyone's exact figures, and models differ significantly. Some ranges overlap more than others; some designs are adjustable across a wider window.
The all-up weight is the one people get wrong
The weight the certification cares about is everything flying: you, clothing, boots, helmet, the harness itself, the reserve, instruments, water, and anything in the pockets. Not your bathroom-scale figure.
The gap between those two is routinely 15–20 kg, which is enough to move someone from "within range" to "above range" without any change in the pilot. Weigh the whole assembled kit rather than estimating it, and recompute whenever you add something — a heavier reserve or a full water bladder is exactly the kind of change nobody revisits.
Fit is a flying matter, not a comfort one
It is tempting to treat harness fit as a comfort question, and comfort is genuinely part of it on a long flight. The larger issue is that the harness is what connects you to the wing and how you move in it is how you steer.
Weight-shift authority, how the harness responds when you are thrown about, how the protector sits under you and how the reserve deploys are all affected by whether the thing actually fits. A harness that is loose in the geometry does not simply feel odd — it changes the handling.
Which is why this ends where all the gear questions end: the general bands get you to a shortlist, the manufacturer's chart narrows it, and trying it on and getting a check flight with a certified instructor is what decides it. A calculator has never sat in a harness.
Adjustability is not the same as fit
Most harnesses adjust across a useful range — shoulder straps, leg straps, seat depth, back angle, chest strap width. That flexibility can make a marginal size feel acceptable on the ground, which is exactly the situation to be careful about.
Adjustment moves you within a size's design envelope. It does not turn one size into another, and a harness run at the extreme of its adjustment often sits differently in flight than it does hanging in a shop — particularly under load, and particularly when you are being moved about.
The chest strap deserves its own mention: it changes the distance between the risers, which affects how the wing feeds information to you and how it behaves in a collapse. It is a flying adjustment with real consequences, not a comfort strap, and how to set it is an instructor question.
The protector and the reserve
Two components whose behaviour depends on fit. A back protector positioned by a harness that does not fit you may not be where it needs to be in an impact. And reserve deployment — where the handle sits, whether you can reach it in an unusual attitude, how the container releases — is geometry, and geometry is what sizing is about.
Both are worth checking in a hang test rather than assumed from a size chart, which is standard practice at any school and is the reason buying a harness without trying it is a poor idea however good the arithmetic looks.
Second-hand, and what to ask
Used harnesses are common and reasonable, and the sizing question is the same. What is added is the condition question: age of the harness, age and repack history of the reserve, condition of webbing and stitching, and whether the protector is intact.
None of that is visible in a size band, and all of it is worth having checked by someone qualified before it flies.