Hey sorry if this has been asked a lot but i just started doing mythic plus this week and had a question about io.
If i time a 15 fortified for 150 rating, will timing a 15 tyrannical the next week give me 150 as well, or does it only start giving new rating at a certain key level?
You get individual scores for Fortified/Tyrannical keys, which are then compared for a composite dungeon rating.
Rather than adding both together 1:1, Wow weighs the highest by +50% and the lowest by -50%.
If you timed a 15 Fort with no Tyran, that dungeon score would be at least 225.
Ok makes sense, thanks
If you timed a 15 on one week and another 15 for that dungeon the next, it’ll give you a composite score somewhere in the ballpark of 250.
Keldion explained the math much better than I could.
I also forgot to check the actual math on each key level, but you’re right - the base score of a timed 15 would turn out to be 125. Therefore, having timed a Fortified and Tyrannical key at 15 each guarantees that you would have a composite dungeon rating of 250 or better.
The base score for a given key is [5 + Key level + Affixes], where Affixes ranges from 1-5 for each affix on the key. The seasonal affix counts as 2.
E.g. [Fortified] = 1, [Fortified Bursting] = 2, [Fortified Bursting Storming] = 3, [Fortified Bursting Storming Shrouded] = 5
In other words…
2-3: [6 + Key level] * 5
4-6: [7 + Key level] * 5
7-9: [8 + Key level] * 5
10+: [10 + Key level] * 5
Score grows very quickly until the 10s, then levels out from that point onward. It’s rather funny how this system is designed to raise your rating quickly at the start, then grow more slowly over time.
You have it wrong. The higher score is kept regularly. The lower score is halved by 50%. Timing a 15 on both fort and tyrannical gives 225 score.
As of this writing, I have scores of 160 or greater for my timed 22 keys, and 156 for my timed 21 Upper in my Wow armory profile. https://worldofwarcraft.com/en-us/character/us/moon-guard/keldion/pve/mythic
If you want to assume I’m wrong, are you going to point out that the score formula calculation under your method uses x7.5 instead of x5 per level and weighs the lower score by 1/3 of its regular value? Kind of like how 150% is 3x greater than 50%? The end result is still the same.
Look at your profile under raider.io, or mine, or anyone else’s, and mouse over the key numbers in the Fortified and Tyrannical columns. Then take notice of how they are ± 50% of the first number.
Timing a 15 Fortified and 15 Tyrannical for the same dungeon will yield at minimum 250 rating.
I looked into this a while back because a friend was playing two characters and wanted to know what his merged rating was, so I made a spreadsheet (because I’m a dork) 
The way you said it was mostly correct, I think you just forgot a few things. It’s 150 base rating for a +20 for both tyrannical and fortified. The one that is higher is multiplied by 1.5 and the one that is lower is multiplied by 0.5. So if you’ve just barely timed* a +20 on both weeks, you can expect roughly 300 rating (225 + 75).
What gets a bit confusing is how much base rating you get for each key. You’d think it would start at some amount and increase as you go up, which is does, but you also get some bonus rating for each affix you add.
Note that these are after the adjustment of multiplying by 1.5 for the higher rating. Divide each of these by 1.5 to get the base rating.
The base rating difference between each key is 5 points, but each affix adds another 5 and the seasonal affix adds a bonus of 10.
You also get some base rating earned (or lost) depending on how much under (or over) the timer you are. I checked and I seem to recall this was linearly interpolated between that 40% mark mentioned in the wowhead article.
That Wowhead article is basically correct, save for how its calculation method could confuse anyone who looks at their armory profile or Rio and see differing base scores.
It presupposes the 150% weighting on your best key.
Yea it was really throwing me off until I figured out all the values were premultiplied by 1.5. I find it much easier to think of things in terms of base rating and then adjusted rating (multiplied by 1.5 or 0.5 accordingly).
That’s what helps me though, I’m sure this made perfect sense to whoever wrote the article
I have no idea how the scores work but ZERO CHANCE I disagree with this warlock fellow here 
He could be 1000% percent wrong and making stuff up as he goes along and I’d believe him. Could probably convince me the world is flat.
(not saying you are, I’m pretty sure what you’ve been saying so far is correct).
All I know is, 15 timed on both fort and tyrannical (one-chest for both) will give you a score around 250, because Keystone Master requires 2000 overall rating, 8 dungeons x 250 for each = 2000.
Hi everyone. Cheching my ratings on raider io i see that my +18 get 141.2 and 141.6. Calculating on left time seems that they divide left time/150 to add to base score.
The score rating variance is based on percentage of time above or below the par time, up to 40%.
Keys timed: Base rating += (Margin / 40) * 5
Keys untimed: Minimum(Base rating, 170) -= 5 + ((Margin / 40) * 5)
You completed Iron Docks 18 with 9.9% under time, so your score was accordingly boosted by an additional (9.9/40)= 24.75% of a single key level (5).
I’ve finished a +25 Junkyard with 40.8% additonal time, and have earned the maximum score possible off of that specific key level - 175 plus 5 for the bonus time.
For keys that failed to time, you can still earn points if you finish within 40% of the par time.
EDIT:
Untimed keys now have an effective ceiling at +20, or 170 base rating.
https://us.forums.blizzard.com/en/wow/t/mythic-difficulty-and-rating-adjustments/1391432
Presumptively, base rating scores in Dragonflight will resemble this formula.
10+: ([Key level - 10] * 7) + 100
Just as a reminder, before anyone goes to assume that Blizzard is unnecessarily inflating M+ ratings with this change, remember the following.
These first few weeks will be spicy. If the KSM target of 2000 rating doesn’t change, then you’ll grab the achievement with a mix of 13s and 14s.
Update for Dragonflight Season 2 scoring!
Because of the way affixes were changed, base scores are going to be slightly different. The +4 affix category now is applied at +7, and previous +7 affixes are now applied at +14.
2-6: [6 + Key level] * 5
7-10: [8 + Key level] * 5
11-13: ([Key level - 10] * 7) + 90
14+: ([Key level - 10] * 7) + 100
The scores are weighted by the presence of affixes, so in order to get the ratings jump, you will need to get higher keys. This stretches out the bottom end, but by +14 and above, the scoring will be identical to Season 1.