The current popular bouldering rating system is the "V" system, devised by John "Vermin" Sherman, hence the "V." This system starts with VB for any problem easier than 5.10, then V0 for 5.10 and on up to the current extreme of V14 or V15. The following is the basic conversion between the V-system and the YDS:

V0-(or VB) = 5.9
V0 = 5.10-
V0+ = 5.10+
V1 = 5.11-
V2 = 5.11
V3 = 5.11+
V4 = 5.12-
V5 = 5.12
V6 = 5.12+
V7 = 5.13-
V8 = 5.13
V9 = 5.13+
V10 = 5.14a
V11 = 5.14b
V12 = 5.14c
V13 = 5.14d
V14 = 5.15a
conversions from

It's important to remember that a bouldering route is usually rated based on its crux move, and it may have only one crux move. Climbing routes are usually longer than bouldering routes, and may have three or four crux moves. So while you may be able to complete a V5 bouldering problem, you may have trouble completing a 5.12 route.

Keep on climbing!