What is your IV threshold for evolving Pokemon?

66+ if it's high level and its stats are well rounded, or for prestigers. 80+ if I'm going to stick it in gyms or something. I have a bit of evolution addiction so I don't always have candy for power-up, high level in 'mons compensates for that. I like 82+ but this site's fanaticism over IVs makes me feel rebellious.

usually at least 80 but sometimes if it have high cp good attack is enough for me. if i have already good pokemon of kind with good moves i evolve only if they are almost perfect iv or if i have lot of candies

80+ usually but I can go for less if the mon is rare in my area or I'm not gonna use it at all (I evolved Skiploom iwth 40% IV just for Pokedex)

For me it increased with time and varies with pokemon :).
Defenders:
Blissey - 96 IV or 15 Attack and above 84 IV
Snorlax - above 80 IV, in fact his max CP > max CP of my 80 IV one, that has only 11 for Attack (on par with a 89 IV Rhydon)
Rhydon - 89 IV and Mud Slap
Gya - 93 IV

Attackers/Defenders:
Vape - 96 IV
Dragonite - 100% (I have a 96, a 98 and a 41 one :) );
Tyra - 93 IV (I have a 91 one) but 0 candy (the first one still eats them to grow).
Exe - for defence above 96 IV; for attack I just evolve a lvl 29, 71 IV one and will power up a bit since he got Solar Beam
Espeon - I did 2 above 84 IV, now probably a 93 one I will walk for Espeon; if higher I will gamble for Vape
Donphan - I don't care

Other attackers - right now the ones that matter came quite easy with >= 91 IV (except for execcutes), so that is somehow a threshold I find myself using. I still prefer to power up from lvl 20 to lvl 30+ a 91+ IV instead of using a 71 IV lvl 30.

At this time I really don't miss anything, I can think only at 5 moves marginally better in theory than what I have:
1. DT/O Dragonite (98 IV Hurricane)
2. C/Dp Matchamp (98 IV Close Combat)
3. Es/SoB (just got a BS/SoB one)
4. Fs/O Flareon (98 iv Charizard with same, other 2 Flareons either with FS or Overheat, various Arcanines)
5. P/Hb Blissey for attack (91 iv, 15 Att P/DG ) if I ever decide I need one in lineup :).

depends on the mon.
for the really important stuff IV>CP and generally 88.9% +; for things like Karp and eevee 93% +

for less important things CP>IV generally will still aim for wonders but a level 29 in the 65-75 zone is a sure bet (face it you will never get around to spending the dust on it so the cp it achieves will be higher then a perfect level 20 you never get around to levelling )

non evo's with good moves might get powered up anyway 65% ZH/BS snorlax, 75% wild caught 1900cp DB/DC dragonite

IVs are also relevant for attackers because the damage formula (found here: https://pokemongo.gamepress.gg/damage-mechanics) factors IVs in.

However:

1. damage rounding can make mons with different IVs deal the same amount of damage - in other words a 15/15/15 Dragonite may well perform identically in battle to a 12/12/12 Dragonite (with movesets and levels being equal).
2. even if the IVs cross the rounding 'breakpoint' and make a difference to the damage delivered, in practice, the reality is that you may shave off 2-5 seconds from a battle if at all.

So good IVs are good to have for attackers but moveset and level are far, far more important.

In fact, to optimise play and save candies and stardust, you should evolve high level attacking mons instead of high IV ones.

Ideally if you have a high level and high IV one then that would be the best, but if you had to choose between a high IV one (but low level) or a high level (but low IV), you would almost always be better off going for the high level, low IV attacker.

Usually 88+ but it depends...

I can't get further than 86% for Oddish, Poliwag, Nidoran.

And for example I found an exegg 68% but 5000CP as it was high I evolved.. since I have 600 candy.

It doesn't make any sense to use a single threshold for every Pokémon. High IVs matter for mons with high max CP, for the rest, moveset and level are far more important. I have a few 100% mons that will be stuck on level 20 (or lower) forever because they have bad moves and/or are not worth powering up simply because I have the same mon with the same moveset but close to level 30.

I try to go for 67% or higher but some times I get carried away with rare pokemon.

sorry but i only catch 100iv which is very common here in my place becoz we have a great scanner/trackers here

91%, the only exception was my first Lapras was only 89% and it had good moves so I invested in it. But as it turned out, months later I have 2 better Lapras (100% and 93%) but no candy to power them. Oh the irony!

91.1% or greater.

With prestigers high IVs are not necessarily the best. In most cases 66% IV 0.15.15 ADS is optimal. The reason is because of how CP is calculated ATK has the greatest impact on CP and therefore have the lower levels with highest CP. As was mentioned a higher level with 0 attack IV and a lower CP will make for a stronger prestiger in most cases. I think for high atk stat mons like starmie looking for 0.15.15 mons will yield much tuffer prestigers. With how difficult training is now these little differences can help. Im a bit lazy at level 37 and lack the IV checking energy I had at lower levels so when I look at two prestige mons candidates for evolution with similar CP I will usually glance at the level and pick ones that say Def/Sta are highest and avoid ones that say the ATK stat is the highest.

91+ evolve asap
82-88 evolve if I have 2x the candy I need and trade bad movesets.
<82 if I have 3x the candy I need and trade always.
Minor exceptions for rare good pokemon.