Not all structs align to words. struct alignment is actually tied to the largest element in the struct (up to word size). For example:

// alignment = 1
struct abc {
    uint8_t a;
    uint8_t b;
    uint8_t c;
};

// will compile just fine
_Static_assert(sizeof(struct abc) == 3, "unexpected size of struct abc");  

// alignment  = 2
struct def {
    uint8_t a;
    // will pad a byte here
    uint16_t b;
};

_Static_assert(sizeof(struct def) == 4, "unexpected size of struct def");  

// alignment  = 8 (assuming 8 byte pointer)
struct ghi {
    uint8_t a;
    // will pad a 7 bytes!
    void* b;
};

_Static_assert(sizeof(struct ghi) == 16, "unexpected size of struct ghi");  

By the way, if you are ever unsure, _Static_assert is your best friend (I believe you need C11 for it though). If that assert was false, it wouldn't compile.

Also, there are some other convenience macros/functions to take advantage of for these types of things. There is alignof, __alignof or __alignof__ depending on your compiler. So you could do alignof(struct abc) to have access to the alignment attributes. There is also offsetof in <stddef.h> that you can use to get the byte offset of individual struct members: int x = offsetof(struct def, b);.