Your scale and your fitness account, actually in step
Weighbridge copies weight and body composition from your Withings scale into Garmin Connect, on its own, within seconds of you stepping off. Delete a bad weigh-in in the Withings app and it disappears from Garmin as well — which almost nothing else does.
Free while Weighbridge is in preview. No card, no subscription.
- Automatic — a weigh-in reaches Garmin in seconds, with nothing to open
- Deletions propagate, so one bad reading does not haunt your charts
- Nine fields, not just weight
- Your Garmin password is never stored
Deletions propagate. Almost nothing else does that.
Everyone weighs themselves holding a towel once. In most sync tools that reading is permanent: you can delete it in the Withings app, but the copy already in Garmin stays, and Garmin's own history is tedious to edit. Weighbridge notices the measurement is gone and removes it from Garmin too.
This is harder than it sounds, which is why it is rare. Withings does not announce deletions — a deleted measurement simply stops appearing. There is no event to react to, so Weighbridge re-reads a whole window of your history on a schedule and compares it against what it has already written. The difference is the deletion.
What gets synced
Everything your scale reports that Garmin has somewhere to put:
- Weight
- Body fat percentage
- Muscle mass
- Bone mass
- Hydration
- Visceral fat index
- Basal metabolic rate
- Metabolic age
- BMI
Hydration needs converting on the way through — Withings reports it in kilograms and Garmin's field is a percentage. Getting that backwards is the single most common bug in home-made sync scripts, and the reason a lot of people's Garmin hydration reads about 40.
Why Garmin's muscle number looks different
Withings and Garmin use the same words for different quantities. Withings reports lean soft tissue — everything that is not fat or bone, organs and body water included, typically 70–84% of body weight. Garmin's field is skeletal muscle alone, nearer 30–45%. Copying the number across unchanged, as most tools do, overstates Garmin's metric by roughly 1.8×.
Weighbridge converts it, so the figure in Garmin means what Garmin says it means. The conversion is an estimate from a population average, and you can switch it off in one click if you would rather see the raw Withings number in both apps. Whichever you choose, the value stored here and shown on your dashboard is always the untouched one from your scale.
How it works
- 1
Connect Withings
One tap through Withings' own sign-in page. Weighbridge never sees your Withings password — it receives an access token you can revoke from Withings at any time.
- 2
Link Garmin
Garmin has no official way to authorise a third party for writing, so this step needs your Garmin credentials once, to create a session. They are used for that and discarded; only the resulting session token is kept, encrypted.
- 3
Step on the scale
Withings notifies Weighbridge, which writes the weigh-in to Garmin within seconds. A daily sweep re-checks the last week to catch anything edited or deleted in the meantime.
About your Garmin password
Weighbridge needs it once, at linking time, because Garmin publishes no way to grant a third party write access — no OAuth, no app permission, nothing. The credentials are used to create a session and are then discarded. Only the session token is stored, encrypted with AES-256-GCM, and it is what gets used from then on.
- Your Garmin password is not stored, not logged, and not recoverable from anything Weighbridge holds.
- Two-factor authentication is supported — the code is requested during linking, in the browser.
- Withings uses OAuth, so no Withings password is ever seen at all.
- Weight and body composition are health data. They are stored in the EU, never sold, and never shared with anyone but the two services you connected.
- You can export everything as JSON, or delete your account and every measurement with it, from the app.
Questions people actually ask
Does Garmin not have a way to import weight already?
Not from another app, no. Garmin's official Health and Activity APIs are read-only, Connect IQ apps cannot write body composition, and the partner programme that grants read access costs thousands per year. You can type a weight into Garmin Connect by hand, and that is the whole of it. Weighbridge does what the Garmin Connect website does when you submit that form.
What happens when I delete a measurement in the Withings app?
It is removed from Garmin too, usually within a day. Weighbridge re-reads the last week of your history on a schedule and compares it against what it has already written; a measurement that has vanished from Withings gets deleted from Garmin. If you want it gone sooner, press Sync now.
How quickly does a weigh-in reach Garmin?
Seconds. Withings sends a notification the moment your scale uploads, and Weighbridge acts on it straight away. Nothing needs to be open — not the app, not your phone.
Do you store my Garmin password?
No. It is used once, at linking time, to create a Garmin session, and then discarded. Only the session token is kept, encrypted. Garmin gives third parties no other way to write to an account, which is an unsatisfying answer but an honest one.
Does it work if I have two-factor authentication on Garmin?
Yes. Linking asks for the code Garmin sends you, in the browser, at the moment it is needed.
Which scales work?
Any Withings scale that reports to Withings Health Mate — Body, Body+, Body Cardio, Body Comp, Body Scan and the older WS series. Weighbridge reads from your Withings account rather than from the scale, so whatever your account shows is what it can sync.
How far back can it import my history?
Two years. The first time it runs, Weighbridge imports up to two years of past weigh-ins from Withings.
Why is the muscle mass figure different in Garmin?
Because the two companies measure different things and call them the same word. Withings reports lean soft tissue, around 70–84% of body weight; Garmin's field is skeletal muscle, around 30–45%. Weighbridge converts between them so Garmin's number means what Garmin intends. Tools that copy the value across untouched leave Garmin showing a figure roughly 1.8× too high.
Can I turn that conversion off?
Yes, in settings, and you can apply the change to weigh-ins already in Garmin rather than only to future ones.
Does it sync the other way, from Garmin back to Withings?
No. Weighbridge writes to Garmin only. Weighing yourself on a Garmin Index scale and expecting it in Withings is not something it does.
What if Garmin changes something and it stops working?
It is possible — Garmin publishes no supported interface for this, so the one being used can change without warning, and has before. Weighbridge is built to fail visibly rather than silently: your account gets flagged, the dashboard says so, and a notification tells you.
Do I need to leave an app running?
No. Everything happens on the server. Your phone can be off.
Where is my data, and can I get rid of it?
In a PostgreSQL database hosted in the EU. You can download everything as JSON from the app at any time, and delete your account with one action — measurements, tokens and provider connections all go with it. Weigh-ins already written to Garmin stay in Garmin; once the connection is gone there is no way to reach them, so delete those first if you want them gone too.
Is this made by Garmin or Withings?
No. Weighbridge is an independent service, not affiliated with, endorsed by or sponsored by either company.
Try it this week
Connect both accounts in about two minutes. If it is not doing something useful, disconnect them again — nothing is kept that you did not put there yourself.