How much ammo can the m1 garand hold?

The standard production M1 Garand uses an 8 round en bloc clip.

Some variations were made which fed from detachable box magazines, but they never went into large scale production. One model used a 20 round BAR magazine, one model used a magazine which was compatible with the BAR, but could not use a BAR magazine, and several variants used proprietary magazines.

Argentine Garands were converted to 7.62x51, and were refitted to use a Beretta BM-59 magazine. Brazilian Garands were converted to 7.62x51, and were refitted to use a FN-FAL (metric) magazine.