An iPhone scan that gives armwrestlers, coaches and researchers a number they can trust week to week — instead of a bucket of water and a guess. Below is a real hand, reconstructed from 76 photos and measured in the lab.
123Hand turns an iPhone Pro into a measuring device. Two taps set the wrist plane, a guided orbit captures the hand from 34 positions with metric depth in every frame, and the phone rebuilds the hand as a solid mesh, cuts it at the wrist, and reports the volume in cubic centimetres. Not a medical device. No health claims. Just a repeatable number.
You tap once on each side of the wrist. The phone measures the width live and draws the cut plane there — the same plane every scan, so growth is growth and not a different cut.
Orbs appear around the hand on three rings. Move the phone through each one and it fires a 12-megapixel frame with the LiDAR depth map embedded — that depth is what gives the reconstruction real-world scale.
The phone reconstructs a watertight hand, finds the wrist plane, and integrates the volume in cm³ — on device, no upload. A plausibility gate (150–1200 cm³) refuses to show a number it doesn't believe.
He told us his number on WhatsApp before the mesh existed. The lab measured the reconstruction without knowing it, with zero calibration. The two numbers are below.
| Volume | 503.3 cm³ | enclosed volume distal of the wrist plane |
| Wrist circumference | 207.4 mm | perimeter of the cut plane (area 2,697.5 mm²) |
| Hand length | 215.9 mm | wrist plane to the tip of the middle finger |
| Thumb pad thickness | 48.1 mm | the number Ryan flagged as "a big one" |
| Palm height | 64.6 mm | thickest point of the palm above the table |
Honest caveat: this first scan's cap was not fully watertight and the wrist cut was placed by a person on the renders, so a point or two of that agreement is luck. The app now sets the cut from your two taps and seals the mesh itself. The method is the same; the hand is the same; the number stands.
Hand volume moves 1–3% within a day. Water displacement scatters by 2–4% between readings. If the thing you are chasing is a few percent a month, the instrument has to be quieter than the signal — and the ritual around it has to be the same every time. So the protocol is part of the product.
Scan at the same time of day, nothing heavy in the 12 hours before.
Let the fluid settle before you set the wrist.
The untrained hand is your control.
The difference between the two is your noise floor. In the lab it was 0.17%.
Growth measured against a moving cut isn't growth. The two taps fix it.
Ryan Rossner is a longevity researcher who works with top armwrestlers on growing hand volume through biological interventions. He asked a question on WhatsApp. Kenny at 123 Division answered with an instrument, for free.
A 25% gain, measured weekly or monthly, charted per subject. That is the job: make the progress scientifically chartable in a standardized way, and give them a 3D image they'd actually want to look at.
The thread, verbatim, from the exported chat. His "Mine is 500" is the number the scan above was checked against.
About two minutes from opening the app to reading the volume. Every scan is filed under the person it belongs to, so the next one lands on the same chart.
Pick who is being scanned. Scans and water tests both file under that name.
A rubber-band line with a live centimetre readout. The cut plane and a capture box size themselves from it.
Brace the forearm, spread the fingers, hold still. Move the phone through each orb on three rings — it shoots for you.
The mesh builds on device from the depth-embedded frames. Photos and meshes never leave the phone.
Volume in cm³ with the measured view. Two or more scans and you get the chart: Δcm³, Δ%, first mesh beside latest.
