The following are average ranges for your typical amateur church choir music, based on my 20-odd years' experience in choral singing:
- Soprano: Bb3-E5, with optional notes up to B5 (and you very rarely see much above G5)
- Alto: G3-C5, primarily staying between C4 and B4 (songs requiring altos to sing higher than C5 generally do so for a specific effect, or because both first and second sopranos are even higher)
- Tenor: C3-E4, with certain pieces having "occasional" Fs and Gs
- Bass: F2-C4, with optional notes from C2-E2 and the occasional D4-E4
These are the standards for contemporary Christian choral works, intended for volunteer choirs in English-speaking North America. Older works typically trend a bit higher in each part, and/or "stretch" each part across more of its range. This is primarily because said older works were intended for choristers who spent more time training than the average two-hours-a-week mainline church choir does today, and also because these works run the gamut of regional influences, from British and Italian which typically trend higher, to Slavic, German and Russian which typically trend lower, especially in male voice.
For high-level amateur and professional choral singers, those "optional" notes above become requirements, thus increasing the repertoire the choir is able to sing. Professional groups also start to formally differentiate between a true soprano and a "mezzo-soprano", and likewise between true tenors, baritones, and true basses, which is reflected in the scoring being expanded from four-part harmonies to six, eight or more. The average volunteer choir often doesn't have that luxury; walk into most mainline churches (that don't pay their choir) and you'll find a group of about one to two dozen, about two-thirds women, made up primarily of women you'd class as mezzo-sopranos and men you'd call baritones, with a scattering of true sopranos and basses, and maybe one or two (if you were lucky) guys you'd deem true tenors. In those cases, if you can sing the notes you get the part regardless of your tessitura.
For soloists, you start venturing into "colors" of voice part that have often-subtle but significant differences in range, such as a dramatic soprano versus a coloratura or soubrette, or a lyric tenor versus a dramatic tenor, or a lyric baritone versus a bass-baritone versus a true bass versus a basso profundo ("Russian Bass"). These "colors" typically have a slight change in range compared to each other.
For more evidence of what each voice part should be able to sing, look at the traditional clefs used for each part. The treble clef (a "treble" is technically a preadolescent voice aka a boy or girl soprano, but the range is similar to the average mature female soprano) allows notes from D4 to F5 without leger lines. The "alto clef" (rarely used any more in voice but still seen in instrument scores such as for viola and english horn) centers on Middle C and extends from E3 to A4. That's considered a bit low for an alto tessitura nowadays (it was originally intended for the post-pubescent falsetti "male altos" of all-male choirs), but a true alto should still be able to hit all of that in full voice. The true tenor clef is only a third lower than the alto clef, ranging from C3 to F4 (again it's rarely used anymore for voice but is seen in instrumental parts such as for trombone, baritone horn and bass clarinet); modern tenors sing on the treble clef transposed down an octave. The bass clef ranges from F2 to B3. In all those cases, pretty much anyone who walks in off the street who is comfortable singing any note within any of those clefs would be labelled as being in that voice part (with two exceptions; a woman comfortable singing a tenor range or lower is a contralto, and a man comfortable singing alto or higher may be called a countertenor instead of a male alto).