Reconstitution math for lab handling — a worked example

The single most-asked handling question, worked end to end. This is bench math for documenting a stock concentration — nothing about consumption.

Say a vial contains 10 mg of compound and you add 2 mL of bacteriostatic water. Concentration = mass ÷ volume = 10 mg ÷ 2 mL = 5 mg/mL. That's it. That number is what you write on the label and in the notebook.

Change the water volume and the concentration changes inversely: same 10 mg in 1 mL is 10 mg/mL; in 5 mL it's 2 mg/mL. Pick a volume that makes your concentration a round, easy-to-record number and your future notes will thank you.

Clean worked example. The only thing we'd underline: pick the diluent volume so the resulting concentration is a round number you can record without rounding errors. The math is trivial; the documentation discipline is the actual skill.

Units pedantry, lovingly: keep mg and mL consistent throughout and your mg/mL falls out clean. Most "my math is wrong" posts are actually "I mixed up my units" posts.

The inverse relationship (more water = lower concentration) is the bit that finally clicked reading this. Wrote the 10 mg / 1 / 2 / 5 mL examples straight into my notebook.

That's exactly the goal — make future-you's records effortless. If your concentration is an ugly decimal, change the diluent volume, not your handwriting.

Want to join the discussion?

Related discussions

Summer shipping: how cold are your gel packs on arrival?

Picking a diluent volume that gives a round concentration

The −20 °C vs −80 °C argument, again (with feeling)

Vials arrived warm after transit — how are you logging it?

War story: caught a mislabeled vial before it hit the bench

PRECISION. PURITY. PERFORMANCE.

Research peptides. Third-party Certificates of Analysis (Janoshik Analytical & Freedom Diagnostics) are published on the website. Supplied strictly for laboratory research use.

Shop

All research compounds

Price list

Where to buy peptides

Research