-First, a normal attack, which usually deals a high amount of damage; then half of that first hit,
and then finally two attacks that add up to the second hit. For example, 300-150-70-80.
-If the first hit misses and the second one hits, the 3rd and 4th hits will each deal half of that damage.
For example, 0-300-150-150.
-If the first two attacks hit 0-0, the 3rd and 4th will perform as regular hits.
For example, 0-0-300-300.
-If the claws hit 3 initial zeros, the last hit (if it hits) will have a 50% damage boost;
e.g.: 0-0-0-450.
-If the first three attacks fail, and the fourth attack also "fails", the fourth attack almost
always hits a low number instead of a 0; approximately between 1 and 7 lifepoints.
A player with protect from melee, divine/elysian shield, 90+ defence,
or with the Staff of Light special attack active can sometimes completely defend against dragon claws.
Taken from -> http://www.rune-server.org/runescape...t-formula.html