I'm a little confused because this isn't tagged as a bard spell, but books and independent sites (roll20, dnd5e.*******) list it as a bard's spell.
Is there a reason it has been removed?

Quote from Lancefrii >>

4d6+1d4+mod sounds like a lot, but being large also has drawbacks. A medium creature needs 2 or 4 creatures to flank it, but a large creature can be flanked by 3 (2 on one side, one on the opposite side) so it IS technically easier to get flanked. Cover just big enough for a medium creature doesn't cover a large creature. Covering more space means you can be included in AoEs easier. A spell like Lightning Bolt, basically fireball in a line, might have missed you when lining up with another target, but being chunky put you in its path.

 

And what if someome takes your weapon? Or just makes you drop it? It loses its extra size, and probably doesn't come back under the effects of the spell when you pick it back up.

 Is flanking still a thing?

I managed down to 3/800 of an inch rules as written.

Quote from deathofhell24 >>

Quote from Nereze >>

 If you use this on a mount and your riding it, do you grow too?

 No. Only the target increases a size, not you. of course, you could use hombrew to change that.

 There is of course, find stead...

This may well not get answered but if your Rune Carver Fighter has just used Giant's Might to become a size Large, if enlarge is used on them would they then become Huge? 

Quote from Crockov >>

This may well not get answered but if your Rune Carver Fighter has just used Giant's Might to become a size Large, if enlarge is used on them would they then become Huge? 

 Yes.

The area says 30 ft. for spell effect.

Quote from deathofhell24 >>

Quote from Nereze >>

 If you use this on a mount and your riding it, do you grow too?

 No. Only the target increases a size, not you. of course, you could use hombrew to change that.

 Actually, in the Player's Handbook, 'find steed' says if you target you or your steed with a spell, it can affect both of them. So i think this spell would work for that.

I'd like to know your process! I got 0.075 like this:

Kobold PC at min height = 27in

Play a Wild Beyond the Witchlight campaign and have a fey steal 3in for a plot hoot = 24in

Have the Wand of Wonder magic item half your size (4% chance each use) = 12in

Eat one of Chucklehead's shrinking candies = 6in

reduce, potion of diminution = 1.5in

go down the secret passageway in area B9 of Bavlorna's Cottage, shrinks you x20, =0.075in

For big sizes, I got this: Potion of giant size for huge (32feet) x Potion of growth x enlarge x Chucklehead's growth candy x Wand of Wonder x Wild Magic Sorcerer Surge = 1,024 feet tall

Can we up cast enlarge/reduce?

You can use a higher level spell slot but it won't change the effect.  It does however make it harder to dispel with dispel magic or counterspell if cast at a higher level.

If you cast Enlarge on a Huge Rune Knight to make them Gargantuan do they lose the 5' of reach they get?  The ability states "Moreover, when you use that feature, your size can increase to Huge, and while you are that size, your reach increases by 5 feet."  Since you are no longer Huge it sounds like you would lose the 5' reach even though that makes no sense.  Probably should have read "Moreover, when you use that feature, your size can increase to Huge, and while you are Huge or larger, your reach increases by 5 feet."

all is not lost with runic knight agility to become large from any smaller size. could stack with this for a huge fighter.

Am I the only one who thinks 1 minute of a spell time seems a BIT short for a size altering spell?

Quote from nessi_c >>

I'm a little confused because this isn't tagged as a bard spell, but books and independent sites (roll20, dnd5e.*******) list it as a bard's spell.
Is there a reason it has been removed?

 That's what I've been wondering. I was looking around at other sources about bard spells (since i can't see some of them without having to buy a digital book), when i noticed that in dnd5e that it's a spell that a bard can use, but not in DnD Beyond. Perhaps it was overlooked or something?

Multiclass into Rune Knight Fighter. Use Giant's might and then get enlarged.

unless the dm says you can

look at the rune knight subclass for fighter. it doesnt say you are under the effects of enlarge spell.

so it took a bit but

you can now wrangle a tarrasque

can you make yourself bigger or smaller?

I mean you can't be under the effects of 2 enlarge spells, but you can use the enlarge spell on a run knight fighter for the same effect