Irregular verbs in the future all use the regular the future tense endings, but change the stem. In this category, some -ER verbs drop the vowel from the stem, and then add the regular endings:
DROP VOWEL | ||
poder | to be able to | podr- |
caber | to fit | cabr- |
querer | to want | querr- |
saber | to know | sabr- |