Assuming your in shape and acclimated to the conditions the rule of thumb I'm familiar with was that one-tenth your body weight could be carried with little slowing but increased fatigue. For maximum mobility you want to keep the encumbrance under this level.

(US infantry is often at this level with little more than body armor and boots.)

one-quarter of your body weight is as heavy as you can go and maintain any ability to run. Even a jog for a short time.

One-third of your body weight is as heavy as you can go and walk fast.

One-half your body weight is as heavy as you can go if you want move faster than a crawl.

Note that these expected speeds are over a considerable distance/ time and most everyone can muster up the strength for short bursts of speed.