Obviously you have to juice about 100, then take 1/100 of that volume to achieve the absolute average lemon juice volume for 1 lemon.

Better of course to take the median volume to account for the outliers, but let's keep it simple!

That's two lemons. You'll ruin your recipe

I saw some baby lemons in the store, ignoring the fsct they were the same price as they lay next to the standard ones, I had to buy the baby lemons.

But that is a giant lemon, wow

I've had a lemon tree grown from seed a few years now, it's finally getting branches this summer. Im excited for next year, hopefully I'll get some buds soon!

Just use it to taste. Unless you’re making sodium citrate for cheese sauce (where the correct ratio of bicarb and citric acid is important) you don’t need to worry. Most recipes with lemon juice add it at the end anyway, to preserve the fresh lemon flavour (which gets destroyed by cooking).

Little known fact, all lemons contain exactly the same amount of limonene, it's just more concentrated in the small one.