Why batching a cocktail isn't just "make it bigger"
The core math of batching is the same as any recipe scaling — multiply every ingredient by the same factor — but cocktails have a couple of extra wrinkles worth knowing. Dilution (the water that melts in from ice while shaking or stirring) doesn't scale the same way when you batch ahead of time rather than making drinks individually to order, since a pre-made batch sitting in a pitcher isn't getting shaken with fresh ice for each serving. Many batch-cocktail recipes intentionally add a small amount of water upfront (roughly what individual shaking would have added) to compensate, rather than relying on ice dilution at serving time.
What to still do at serving time
Batching works best for the base spirits, juices, and syrups — carbonated ingredients (soda water, tonic, sparkling wine) generally shouldn't be batched in advance, since they'll go flat; add these fresh to each glass at serving time instead. Similarly, garnishes and any ice should be added per-drink, not mixed into the batch itself.
FAQ
How far in advance can I batch a cocktail? Spirit-forward batches (no dairy, no fresh citrus) often keep well for several days refrigerated; anything with fresh juice is best made within a few hours to a day for best flavor.
Should I batch a large multiplier (50+ drinks) the same way? The math is identical, but consider batching in a couple of separate containers rather than one huge batch — easier to stir/mix evenly and easier to serve from.