# Do you have to beat or equal a DC?

I'm having trouble finding something to clarify this. It's been mentioned in the Difficulty Class section of the DMG (238) that there should be a 50/50 chance that an average person can succeed at a DC 10 challenge, implying you have to beat it. However, I'd always thought that there's a 50/50 chance for an average person to hit another average person, but the chance is really 55/45, since you only have to equal their AC.

This is answered on page 7 of the PHB:

3. Compare the total to a target number. If the total equals or exceeds the target number, the ability check, attack roll, or saving throw is a success. Otherwise, it’s a failure. [...] The target number for an ability check or a saving throw is called a Difficulty Class (DC).

And on page 174:

If the total equals or exceeds the DC, the ability check is a success — the creature overcomes the challenge at hand. Otherwise, it’s a failure...

As for opposed checks (called contests, also found on page 174 of the PHB), instead of rolling against a pre-set DC you're essentially rolling against a DC set by another creature's ability check. In this case you must roll higher than what the other creature rolled in order to succeed and a tie means neither creature wins or losses and the situation stays the same.

The die roll needs to be equal to or greater than the number indicated for success.

1. Compare the total to a target number. If the total equals or exceeds the target number, the ability check, attack roll, or saving throw is a success.
(PHB p. 7; para 3 of section "the D20").