Hit Points

Hit points are the "points" of damage you can take in Halo 3. In multiplayer, players have 45 "health" hit points, and 70 "shield" hit points. Shield hit points and body hit points recharge after a period of not taking any damage; shield hit points begin recharging in 5 seconds, and health hit points begin recharging in 10 seconds. Shield hit points recharge 40 points per second, and health hit points recharge 9 points per second.

Note that, if you do not have full health but you do have shield hit points and your shield proceeds to take damage, your health recharge delay is still reset back to 10 seconds, even though it didn't take any damage.

Damage Values
Several weapons have been given specific values of damage that they do in hit points:
 * The Battle Rifle does 6 points of damage per shot that hits out of it's burst, for a maximum total of 18 points of damage per burst.
 * The Assault Rifle does 7.5 points of damage per shot that hits.
 * Most weapons have melee attack damage of 70. Brute weapons, however, do 72 damage with melee attacks.

It can be assumed that plasma weapons deal significantly more damage to shields per shot than to health per shot, which means that the values of damage done to shields vs. the values of damage done to health may differ by weapon. However, it has never been explicitly stated that this applies to any weapons but plasma weapons.

In addition, the "threshold" of the point where two simultaneous melees can be contested, and both players can be killed as of the upcoming autoupdate, is 26.5 hit points. Because of this, you can effectively override the melee of another person when your melees are at the same time by having 26.5 or more hit points over the other person. 4 shots from an assault rifle can cause this as a result.