Is there a formula, dice mechanic or rule of thumb to determine an NPC's glory? For instance, I want to determine the Glory for Kings Octa and Eosa on p.112 of the Book of Uther.

There is a rule of thumb in BotEntourage, but it is not a very good one when you start talking about specific people, especially Saxon Warrior-Kings. It was designed more for ordinary vassal knights who might very occasionally become Famous, but usually only if they were older and officers for many years, not for warrior kings and great heroes.

I am not even sure why you'd need the exact Glory? I'd say both are Famous (8000+) and leave it at that.

If you wanted to estimate it, both are Kings and Wotanic, so that should be good for 200 Glory per year, passive Glory. I wouldn't be surprised if they'd rack up another 100 for consumption or other such things. They have both been active since mid-460 at the very latest, so that is about 20 years by the time they show up in 464. So simply by passive Glory alone (assuming they have been Wotanic all that time), they should have earned 6000. Assuming the Saxons get the same Glory for the titles as well (and why not), they should have gained 1000+200+200+200+200 = 2000 for getting the title of a king. That already brings us to 8000. Since no mere milksop would become a king of a warrior people like the Saxons, and they certainly would have been racking Glory from leading raids, wars and fighting in both, something like 4000 Glory would seem reasonable to add. So I'd say they are both somewhere around 12000, give or add a couple of thousand. Call it 12000 + (1d20-10)*20.

Actually, when you take into account the Marriage Glory, it probably should be closer to 12000 + 1d20*20.

Thanks Morien, that helps. I am plugging the NPCs into a module for Fantasy Grounds and the completist in me wants to enter full stat blocks for all the major NPCs. Also, I want to determine NPC glory to be able to set Glory Won values...just in case!

Well, the Glory comes in only at 1% level, so even if you are off by a thousand, it is just 10 Glory difference.

I tend to use the old 4th edition Glory awards, so for me, knowing the category is enough. :) (Although I will say that at the higher level, the 4th edition Glory Awards seem a bit... excessive.)

As for the KAP 5.1 edition Glory award calculation (which I think is missing from the main book, and one needs to check the errata on Greg's page), I have some problems with it. But it is more of a house rule -oriented discussion, I will just post it there:
http://nocturnalmediaforum.com/iecarus/forum/showthread.php?2615-Alternative-combat-Glory-awards&p=22388#post22388

My rule: the NPC needs to have as much Glory as needed to provide suitable antagonism to the player-knights. One of the player-knights was poised to be the best knight in Salisbury so when the time came and Robert, son of Roderick, was invested as knight, that PK would be the one to lead the ceremony. However, there was another knight who was also the best knight in Salisbury. He had as much Glory as the PK. Why? It was entertaining. It provided a suitable antagonist to the PK and motivated him to go the final distance to become the best knight. It turned out to be something of a rivalry between them.

Other examples: Will the player recognize the knight he just jousted? How much of a bonus do I want him to have. +4? Good, then the knight has 4100 Glory. Do I need someone to be known throughout Logres? I give them the appropriate Glory. It's all rather arbitrary and following the whims of the campaign. I don't do math. The players are none the wiser and all goes according to plan.