How is smithing calculated? I'm so confused by these results

[Savage Matt]

I noticed with a Skyforged Steel Sword (as example) that my smithing boosting items apparently don't stack or even offer the improvement they say alone? :S

My boosting items are all for "weapons and armor can be improved 20% better"; Ring of Minor Smithing (12%), Steel Gauntlets of Major Smithing (17%), and Necklace of Eminent Smithing (20%).

The armour results I'm getting are:
unimproved n/a: 32
improved no boost 0%: 51
RoMS (12%): 51 (should be 52?)
SGoMS (17%): 56 (should be 52 or 53?)
NoES (20%): 56 (should be 52 or 53?)
RoMS + SGoMS (29%): 56 (should be 53 or 54?)
RoMS + NoES (32%): 56 (should be 53 or 54?)
SGoMS + NoES (37%): 56 (should be 54?)
RoMS + SGoMS + NoES (49%): 56 (should be 55?)

Really, what is going on?

[Trigger]

what is your game level

[Trigger]

have you used any perks on your smithing tree yet ?

[Savage Matt]

I have the first three perks going up towards the right (heavy armor side up to orcish) and arcane smithing. My smithing level is 64.

[Brandybuck]

Lots of info here: http://www.uesp.net/wiki/Skyrim:Smithing

[Bomb Bloke]

In a nutshell, the skill doesn't directly relate to the damage/protection figures of your weapons/armour. Instead, it defines the "improvement level" you can reach, and that defines the damage/protection figures.

With 64 smithing plus the steel perk, you should be achieving Flawless level. It looks like your enchantments are currently able to take that to Epic. You won't see another increase in stats until you hit Legendary.

It's worth noting that potions can also be used to boost smithing. You could furthermore enchant a chest piece, hunt down the Notched Pickaxe, and/or get the Sallow Reagent Black Book.