Several regular countable nouns ending in f have
special plurals: they change the f to v and then
add -es:

calf / calves
elf / elves
half / halves
knife / knives
leaf / leaves
life / lives
loaf / loaves
scarf / scarves
self / selves
sheaf / sheaves
shelf / shel ves
thief / thieves
wolf / wolves

Several regular countable nouns ending in f
make their plurals with either -ves or -s:

dwarf / dwarves (dwarfs)
hoof / hooves (hoofs)
staff / staves (staffs)
wharf / wharves (wharfs)

Many regular countable nouns ending in f
make their plurals by adding -s:

belief / beliefs
bluff / bluffs
brief / briefs
chief / chiefs
cliff / cliffs
cuff / cuffs
gaff / gaffs
muff / muffs
puff / puffs
roof / roofs
whiff / whiffs