Hit Points per Die

Weight (lbs)	Dice Rolled	Range	Average h.p. per HD
up to 10	d2	1-2	1.5
11-30	d3	1-3	2
31-70	d4	1-4	2.5
71-150	d6	1-6	3.5
151-290	d8	1-8	4.5
291-510	2d4	2-8	5
511-830	d10	1-10	5.5
831-1,275	d4+d6	2-10	6
1,276-1,800	d12	1-12	6.5
1,801-2,500	2d6	2-12	7
2,501-3,500	3d4	3-12	7.5
3,501-4,800	d6+d8	2-14	8
4,801-6,500	2d4+d6	3-14	8.5
6,501-8,700	2d8	2-16	9
8,701-11,500	d4+2d6	3-16	9.5
11,501-15,000	d8+d10	2-18	10
15,000-19,000	2d10	2-20	11
19,001-24,000	d10+d12	2-22	12
24,001-31,000	2d12	2-24	13
31,001-40,000	2d8+d10	3-26	14.5
40,001-51,000	d8+2d10	3-28	15.5
51,001-65,000	3d10	3-30	16.5
65,001-82,000	4d8	4-32	18
82,000-100,000	3d12	3-36	19.5
100,001-120,000	d8+3d10	4-38	21
120,001-150,000	3d10+d12	3-42	23
150,001-190,000	d10+3d12	4-46	25
190,001-240,000	5d10	5-50	27.5
240,001-300,000	3d8+3d10	6-54	30
300,001-380,000	6d10	6-60	33
380,001-480,000	3d10+3d12	6-66	36
480,001 or more	6d10+d12	7-72	39.5

Hit points per die stipulates that when determining a creature's hit points (h.p.), a distinction is made between the creature's hit dice (HD) — which indicates the creature's ability to hit — and the creature's mass. For example, a cockatrice has 5 HD and weighs 98 lbs., while a moose also has 5 HD and weighs 1,220 lbs. or more. Because of its mass, a moose should have more h.p. than a cockatrice, though the latter remains a dangerous creature.

Argues that while the human male and elven female may both have the same amount of experience, they have very different amounts of mass

How many more h.p. is indicated by the table shown. The type of dice rolled indicates the creature's "h.p. per die." For example, the moose described above would have [5-20] + [5-30] h.p. (5d4 + 5d6), an average of 30. Conversely, the cockatrice has [5-30] h.p., an average of 17.5.

As creatures gain in mass, the amount of h.p. gained is staggered so that the amount gained is progressively less per pound. This reflects the amount of comparatively wasted mass of large creatures compared to their fighting ability.

Mass plus Character Level

The table is also indicates the number of h.p. that player and non-player characters possess due to their weight. This rolled number is ADDED to the character's h.p. gained from experience levels. This means that 1st level characters start with more hit points than they'd normally receive in AD&D.

For example, a human 1st level fighter normally gains 1d10 h.p. from their character class. This is adjusted by constitution. For player character, the maximum is given at the start to reflect the character's unusualness. As a human male is likely to weigh between 151 and 290 lbs., he would also start with an additional 1-8 h.p. A human female may weigh less than 151 lbs., but she's certain to weigh more than 71; she would receive an additional 1-6.

It's recognised that these numbers are different for different races and for males vs. females. This is deliberate. Dwarves, elves and so on gain benefits that humans do not; but humans are heavier by and large, which helps compensate for the benefits of other races. On the other hand, if the player chooses to run a female, he or she may be opting for a character with slightly less hit points. It's believed, however, that if a player prefers to run a female, the average loss of a hit point or two won't matter in the long run.

See Also,
Combat
Negative Hit Points