Temperature-loss calculator
Left a vial on the counter overnight? Parcel sat in a hot van? Say what state it was in, how warm it got and for how long, and get an estimate of how much potency is likely left, with a verdict on the vial's condition, from essentially unchanged to likely spent.
What this does: estimates potency lost to heat and time, for dry powder or a mixed vial, using a common rule of thumb that breakdown runs 2 to 3 times faster for every 10 °C warmer (this page uses 2.5). What it does not do: measure your vial, say whether it is fit to use, or tell you what to take; its labelling and whoever supplied it decide that.
1 What state was it in?
Dry powder is far more forgiving than a mixed vial. Once water is in, the clock runs faster.
2 How warm did it get?
Not sure? Pick the warmest it could plausibly have been. Overestimating is the safe direction.
3 For how long?
4 How fragile is it? (optional)
The classes are a rough sorting by chain length and known fragility, not a measurement and not a citation. When in doubt leave it on "typical"; the product's own storage labelling is the authority.
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How the estimate is made: a mixed vial in the fridge is treated as losing about 10% over four weeks at 4 °C (an assumed figure; it is not the 28-day bac water window, which is a separate clock), and dry powder about 2% a year; those rates are scaled up 2.5× for every 10 °C warmer (a Q10 rule of thumb from stability work), and "sturdy" or "fragile" halves or doubles them. Anything quoting a single number for all peptides is an assumption; this page's is stated here so you can judge it. It is an estimate of condition, not a measurement, and never advice about what to take. A vial that no longer looks the way its labelling describes (cloudy when it should be clear, discoloured, threads) has a problem this estimate cannot see; see the cloudy-vial guide and ask whoever supplied it.
Common questions
Is a peptide ruined if it was left out overnight?
By this estimate a mixed vial loses a small percentage overnight at room temperature and dry powder almost nothing. Cold storage from here on limits further loss. Whether the product is still fit to use is decided by its labelling, not by this number. The exception the number cannot see is a vial that has changed how it looks.
My order sat in a hot delivery van for three days. Is the powder still good?
Sealed dry powder is the most forgiving form, and this model puts three days at 40 °C well inside its margin. What to do with a product after a temperature excursion is a question for its labelling and for whoever supplied it; the manufacturer's storage section is the authority, not this page. If the seal was broken or the powder looks discoloured or clumped, that is a different matter again.
Is the result exact?
No. It is a simple model with fixed assumptions, not a test of your vial, and different peptides in the same family vary. Use it to gauge how far a vial has likely drifted from its label, and trust your eyes over the number when the vial looks wrong.
What is the 28-day rule?
Two separate clocks get confused here. The 28 days is a preservative window: bacteriostatic water holds bacteria off for about that long after the first puncture, and the bac water guide explains it. How long the substance itself stays good is a different question with a different answer, covered in the shelf-life guide. This calculator estimates the second, never the first.
The supplies this assumes you have
A fridge thermometer so you know your fridge is at 2–8 °C, a temperature logger if parcels or travel are a regular thing, a travel cooler for the journey, and labels with the date on. The storage guide and the cooling guide are the long versions.