In the fourth edition of Dungeons & Dragons there are no fortitude, reflex or will saving throws any more. Everything is now a fixed defense score. But it is easy to change these defense scores back into saving throws by following these steps:

- Subtract 10 from your fortitude, reflex and will defense. The resulting values are from now on the saving throw modifiers.
- Add 10 to the attack modifiers of attacks vs. fortitude, reflex and will. The resulting values are from now no modifiers any more, but the saving throw DCs you have to beat.
- To make a saving throw the attacked creature or player rolls a d20 adds his "new" saving throw modifier. If he gets higher than the DC he is not affected. If he is below or equal the DC he is affected.

You see, the changes are very simple, because both variant are basically the same thing. The game balance will not be touched by this! I even have a mathematical proof for this. If you interested in it you'll find it below.

Nevertheless, I would not change these defense scores to saving throws:

- They make the game more complicated. That might be okay, if you play for several years and can recite all rules when you are asleep. But in my game group is a relative new player, who has even problems to get the rules right when everything is a defense value.
- The term "saving throw" is already used in the fourth edition. So it might be confusing to use it again for something other. But maybe you can come up with another name?
- With the defense scores every character class gets a similar amount of dice rolls. If you change this to saving throws a wizard would hardly ever roll a dice in a combat, because his spells are attacks vs. fortitude, reflex and will and not vs. AC. That may be disappointing and not very much fun for the wizard!

Now I will give you the prove that both variants are equivalent concerning the game balance: First of all I have to define some variables:

r = random dice roll in the range from 1 to 20 a = the attacker's attack modifier d = the defender's defense value minus 10 or in other words the modifier which is added to the base value of 10

To make a successful attack the attacker has to get a result equal or greater than the defender's defense:

a + r >= 10 + d

This can be also written as (mulitplication with -1, added d + a + 21):

d + 21 - r <= 11 + a

Because r is a random number between 1 and 20, 21–-–r is also a random number between 1 and 20. Therefore we replace this part:

d + r <= 11 + a

Now we only have to change the <= sign to < and we have the formula I've expressed in words as saving throw variant above. This change is possible because a, d and r are whole numbers; we just have to subtract one from the right side for it.

d + r < 10 + a