Do buffs stack?

[dalgo]

If I enter Skull Cavern on a Lucky Day and eat a Lucky Lunch while wearing the Special Charm do these three luck buffs stack or does the game just implement one of them?

[HoloSam]

Yes, they stack. I'm sure you can find some info in the wiki, but the formulas aren't the most simple

[Lurlex]

It's easy. You can only have one food-given buff up at any given time, with the exception of coffee's speed boost ... coffee's speed will stack with say, spicy eel's speed buff. You can tell because there'll be two separate icons with the buff showing at the top of the screen.

As for the other things you mentioned, like the charm and luck of the day, those are static numbers that are in effect from the moment you wake up to the moment you go to sleep, and food-driven bonuses are just added to it.

I don't know of any other way to temporarily boost luck other than food (I wouldn't consider the charm artificial, it's just a point of permanent character advancement), so food is absolutely the only variable you need to consider.

[I Kinda Fail]

I don't know what the actual figures are, but the best way I know how to explain it is...

Let's say your luck has a value of 5 on a neutral day. 4.5 on a bad day, 5.5 on a good day.

The luck charm thing just permanently raises your luck a bit, so you'd have 5.5 on a bad day, 6 on a neutral day, and 6.5 on a good day.

The temporary boosts are more powerful, I think, since they have a "cost" and can run out. So a +4 luck boost might raise you to like 12.5 on a good day, or +1 luck might raise you to like 8.5 on a good day.

I'm not sure if the numbers are accurate, it's just the way I understood it.

[Lurlex]

The luck values are listed in detail here, in the wiki, if you're really curious: https://stardewvalleywiki.com/Luck

It's in decimals on the wiki, but bottom line is that daily luck can be as low as -10% on a bad luck day, and as high as +10% on a good luck day. The charm with the permanent effect is a 2.5% boost.

I think the food buffs are definitely way more powerful than the day-to-day variants, meaning that you can completely turn a bad day around with even the smallest +1 luck buff ... but it's tough to know for sure. Simply "+" a given number doesn't mean much to me -- does that mean it's a whole value, so +3 is actually +300% (huge if true), or is it +0.3, 30%, as the Daily Luck formula deals in values less than 1?

The wiki doesn't clarify the math behind how the food values translate like it does for Daily Luck.