Addons like Foundry Tactical Combat and LUI Extended have a meter... I personally prefer Combat Metrics (it also shows you more detailed information such as dot uptime, group DPS, and the like).

Combat Metrics? Ok I'll take a look

Thanks guys!

Combat Metrics

Seriously, that single add-on teaches you so much about your character and all the cogs and gears that make up your damage and healing.

Keep in mind those DPS meters are NOT overly accurate. Some, only report BASE damage and ignore CRIT damage. Others show CRIT damage. Some completely ignore damage over time like caltrops. Most only show damage per-hit, per weapon. So unless you are standing in the center of a giant mob and spamming steel tornado, the dps meter will appear artificially LOW as it's constantly resetting with each strike.

If you want a better idea of much legit-damage you are doing, get an add-on that lists a numerical value over the enemy's health bar so you can see their actual hit points. Go fight and watch the drops. Do the rough math.

Combat Metrics has issues as well. It has an optional real-time logging viewable from the chat box tab. Problem is, it too won't combine values if you have several things hitting at once, like say caltrops, endless hail, and physical attack, or say you do a heavy sneak attack from stealth, it'll break down each part of the attack like say heavy attack + dual wield heavy + Selistrix + Viper for example if you have sets equipped

DPS values are in all honesty, worthless. It's more important to get an idea of the actual damage numbers based off how fast you are depleting an enemy's health.

To drive the point further, I can hit very low 80k "dps" on mobs with NON Maelstrom weapons and around 70%
crit rating using a dagger and mace. I've yet to ever see a single target take 80k damage from a single hit, though mid to high 30's happen. My heavy sneak attack however from stealth can hit 64k on one strike, though that takes awhile to get up to.