An important distinction to be made here is the difference between range and tessitura. According to The Complete Musician by Steve Laitz,
range is the total span of pitches that a voice can sing; this covers roughly the interval of a twelfth. ... a more comfortable register [is] referred to as its tessitura.
Laitz then provides a chart of SATB ranges and tessituras, reproduced below. "R" indicates range, while "T" indicates tessitura.
Most theory textbooks agree, but there are occasional differences. Note that these textbooks all only discuss the range, not the tessitura:
- Tonal Harmony by Kostka and Payne only has one difference: the lowest pitch of the bass is listed as E, not D. The same is true for Harmony in Context by Roig-Francolí.
- The Complete Musician by Clendinning and Marvin has the entire bass range moved up a step, from E to D instead of Laitz's D to C.
- Harmony and Voice Leading by Aldwell and Schachter has a few differences: the soprano can be extended by one step in both directions; the alto is listed as G to C, with the D an allowable extension; the tenor has a high A as an allowable extension; and the bass is listed as E to C, with both the lower and upper Ds allowed as extensions.
- Harmonic Practice in Tonal Music by Gauldin prefers D to F for the soprano, A to C for the alto, D to F for the tenor, and G to C for the bass. He lists one pitch above and below each range as an allowable extension.