Often times when I am low on mana and somebody wants to gank or something, I will ping that I am out of mana. This number is usually around 13%, but that doesn't really tell them anything. 13% can be 100 mana or 500. there is no way of knowing. A flat number on the other hand would tell a player "Oh, he has 200 mana, that is enough for his ult and q, but nothing else." For the sake of clarity it should be changed.
Maybe both? "Sona has 100 mana (16%) or "Sona has 16% (100) mana" or something.
I agree, a flat amount would be more useful, as bar some exceptions most champions tend to have similar mana costs to their abilities. By contrast, mana pools are much more variable, especially when you factor in items, so knowing which percentage of a mana pool a champion has left isn't helpful when it counts, i.e. when they're mostly depleted but could perhaps still cast a few more abilities in a short fight. Listing both could also be an option, particularly since it would not take that much more space.
if flat numbers... should be 100/500 (20%)
Pinging a ability that doesn't have enough mana usually helps if you have a ability low enough. Though there is always that middle spot where you have enough to case only 1-2 spells where this would help.
Why not both?
Both please. I think my brain can process a few extra numbers in the chat.
Would MUCH prefer Flat Amount & Percent.
yup I can see the % being a problem on some champions such as 
15% mana (800)
I'd much rather see a percent. I don't have every champ's mana usage down. So it saying, "oh he has 200 mana" in no way, shape, or form tells me that he has enough mana for his ult and Q lol. Where as if someone has a low percentage of mana, I know that the probably don't have enough for a rotation. Plus, if they're pinging me they have 13% mana, that is probably a good indicator of "I'm letting you know that I do not have enough mana for this gank to work."
was removed from summoners rift a long time ago.
YES, or atleast both
God forbid u people cant learn how to do math on the fly
To be fair flat ~~percent ~~ number isn't exactly telling either.
You guys can ping your mana? I can barely select the damn thing half the time.
I think its irrelevant. Pinging mana should mean "i do not have enough mana to do anything but auto attack".
