FE6 gives you an overall tactician rank once you beat the game. The ranks are split across 6 different categories, each with a snappy name that has something to do with the game's mechanics. Each rank can vary from A to E, with A being the best. Then based on your ranks for each category, you'll be assigned a final rank that can go as high as SS (Hard Mode only, the Normal Mode equivalent is simply S). The 6 categories are as follows.

If you don't feel like reading the rest of the guide, this table lists what you need to do to an A rank on each category for a true-ending run.

Each chapter has a hidden value that determines how many turns the game thinks you should spend on the chapter. There's a value for each rank A to D. To see what rank you get at the end, the game sums the values for each played chapter at each ranking level. If your total turn count is below the sum, then you'll receive that rank. If your turn count was higher than the sum of the D values, you'll receive an E.

Since the game only cares about the total sum of all the chapters, this means that you can "make up" for a bad chapter by completing a future chapter in a shorter number of turns. The relevant A Rank thresholds for a true-ending run can be calculated easily. The Western Isle route split does not matter in this regard, since they have the same requirements across all ranks.

Each gaiden chapter completed will modify the requirement depending on the gaiden. The table below lists the maximum turn counts for each chapter and each Tactics rank, which can be used to calculate the threshold for a non-true-ending run. Getting more turns than the D rank threshold will result in an E rank.

Combat ranking is pretty simple, it just looks at the percentage of all battles (including enemy phase) that end with your unit killing the enemy unit. The percentage thresholds are listed in the table below (the upper ranges are not inclusive).

Survival ranking is even simpler, it just looks at how many of your units died throughout the playthrough. The death count requirements are listed in the table below (the upper ranges are inclusive).

Experience rank is similar to the Tactics rank, where the game keeps a hidden value for each chapter, but final chapter of the run solely designates what the rank will be. This means that whether or not you do no gaiden chapters or 6 out of 7 on a run, the thresholds for Experience ranking will be the same. Of course, the only two chapters that a run can end on are Chapter 22 and Final (Chapter 25). Hence, we get the following relevant minimum thresholds (going under the D threshold results in an E ranking).

If you are curious and want to see what the unused hidden values are for each chapter, the following table lists the minimum experience total values for each chapter if the game were to end there.

Power rank works in the the exact same way as Experience rank. Each chapter has a hidden value for the minimum total level of your army, but only the last chapter of the run matters. Here's the minumum total level requirements for the bad and true endings (note that promoted units will add 20 to their displayed level, Larum/Elffin and Fae count as non-promoted).

If you are curious and want to see what the unused hidden values are for each chapter, the following table lists the minimum level total values for each chapter if the game were to end there.

Funds also has hidden values per chapter, and again only the last chapter of the run matters. Essentially, it will add your unspent gold with the sum of all of the sell values of your inventory (including character inventory and convoy) and compare that against the minimum values for each rank. Treasure such as the Rapier or the Divine weapons count for nothing.

Unlike Experience and Power, the thresholds are easier to predict. For each chapter, multiply the chapter number (gaidens count as their previous chapter, for example 8x becomes 8; Final counts as 25) by the constants defined in the following table to get the minimum required amount for that rank.

However, due to what honestly seems like a bug in the game, the funds rank doesn't actually use the last played chapter number as the modifier, rather the last shown map's chapter. After you beat the game, there will be some cutscenes that play before the ranking screen is shown. These cutscenes all take you to different maps associated with various chapters. Without spoiling anything, the true ending will take you to Arcadia, which is Chapter 14, resulting in a much lower required funds rankings. If you didn't get the best ending, but unlocked Chapter 23 and beyond, then the last cutscene will differ based on whether Roy has an A support with Lilina. Hence, the relevant thresholds are as follows.

If you are curious and want to see what the unused hidden values are for each chapter, the following table lists the minimum funds total values for each chapter if the game were to end there.