Five prayers are obligatory each day. The number of fard (obligatory) rak‘ahs in each is as follows:
Fajr (dawn) — 2 fard rak‘ahs
Zuhr (midday) — 4 fard rak‘ahs
Asr (afternoon) — 4 fard rak‘ahs
Maghrib (sunset) — 3 fard rak‘ahs
Isha (night) — 4 fard rak‘ahs
That is 17 fard rak‘ahs in total.
The witr prayer
In the Hanafi school the three-rak‘ah witr prayer performed after Isha is wajib; it is not counted among the fard rak‘ahs above.
The sunnah prayers
The sunnah prayers attached to each time (for example the 2 rak‘ahs before Fajr, or the 4+2 around Zuhr) are separate and are not included in the 17 fard rak‘ahs.