Log the first day of your period each cycle (format DDMMYYYY, e.g. 01082026 for 01-08-2026, or leave blank for today). Your average cycle length is calculated automatically from these dates, and every session's cycle phase is then estimated from that automatically.
In the Health app: Browse → Cycle Tracking → Period → the share icon → Export PDF. Upload that file here and we'll pull out the period start dates.
Connect Google Sheet
Make a copy of a Google Sheet, open Extensions → Apps Script, paste the script below in as Code.gs, then Deploy → New deployment → Web app (execute as yourself, access "Anyone"). Paste the resulting URL above.
Add session(s)
Drop one or more files here, or click to choose
PNG/JPG of the Garmin interval table, or a .fit activity file — pick several at once for several sessions
Predicted cycle phases
Overall
By pool & attempt number
Dive prediction
By cycle phase
Session detail
Attempt
Time
Distance (m)
Avg vel (m/s)
Min HR
Avg HR
Max HR
Cells are editable — fix anything the extraction got wrong and the charts update automatically.