This is an irregular verb. It follows the conjugation pattern of the verb abrazar.
PresentPresente
El niño no alcanza el estante alto.
The boy cannot reach the high shelf.
PreteritePretérito indefinido
Ayer alcanzamos la cima antes del mediodía.
Yesterday we reached the top before noon.
FutureFuturo
Si corres, alcanzarás el autobús.
If you run, you will catch the bus.
Imperfect SubjunctiveImperfecto de subjuntivo
Si alcanzáramos la cima, veríamos todo el valle.
If we reached the top, we would see the whole valley.