Sappho didn’t count stresses — she counted lengths. Her stanza is a fixed pattern of long and short syllables, the same shape in every poem: three long lines and a short clinch. It is a rhythm you can walk. Slide the reader (or tap) along the stanza and watch the beat.
The Sapphic stanza, scanned by quantity. Three Sapphic hendecasyllables — the eleven-syllable pattern — u — × — u u — u — — (long, short, long, anceps, long, short, short, long, short, long, long) — followed by a five-syllable adonic — u u — —. That is 11+11+11+5 = 38 syllables in a fixed template that every Sapphic stanza obeys (anceps × is the one free slot). The reader walks the whole stanza; each position reports its quantity. A fail-loud self-check throws unless the four lines are [11, 11, 11, 5] and total 38.
Classical Greek metre is quantitative (syllable length), not the stress metre of English; the anceps is genuinely free and Sappho takes resolutions. The template, the counts and the scansion shown are exact.