Tandem

Two people. One private calendar.

Tandem predicts your cycle, period, and fertile window from your own logged history. It syncs privately between just the two of you using a short pairing code — no accounts, no email, no names.

You can change this later in Settings. Tandem gives general estimates based on standard cycle-tracking methods — it isn't contraception or a medical diagnosis.

Let's set a baseline

You can adjust every one of these later as you log real cycles.

Enter your partner's code

Ask your partner to open Settings → Get a pairing code in their Tandem app, and send you the code however you'd like — text, call it out, in person. It's valid for 24 hours.

That code couldn't be read. Double-check it was copied in full.

Recover your data

Enter the recovery code you saved when you first set up Tandem as the tracker. This links your existing data to this device and replaces access from any other device.

That recovery code couldn't be used.

Tandem
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SMTWTFS
Period Fertile window Ovulation (est.) Predicted period
Tap a date to mark or unmark a period day. Press and hold (or right-click) a date to add flow, symptoms, or a note.
You're viewing a synced, read-only copy of your partner's calendar. Tap a date to see any notes for that day.

Your cycles

Cycle insights

Settings

Pairing

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Recovery code

A long-lived backup code — separate from the pairing code above — that lets you reclaim your data if this device is lost or you switch to a new one. Save it somewhere safe (a password manager or notes app).

Cycle defaults

Update synced data

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Reminders

Get a notification on this device the day before a predicted period, and when the estimated fertile window starts. This is a per-device setting and works best while Tandem is open or running in the background. It only checks while the app is running, so it isn't guaranteed to fire at an exact time.

About your data

Your logged cycle data is stored on this device and synced to a private shared record identified only by a random pairing code — no accounts, no email, no names. Nothing is shared beyond you and the partner you pair with.

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Flow
Symptoms