Frozen Storage MKT Calculator (−20 °C)

Frozen products labelled for −20 °C (typically −25 to −15 °C) must stay below their upper frozen limit; brief warm excursions toward thaw are the concern, so the ceiling (−15 °C here) is what MKT is checked against. The authoritative limit is whatever your product's labelled storage condition and stability data specify — read it off the marketing authorisation, the manufacturer's storage statement or the governing pharmacopoeia, and enter your real temperature history against it.

Yes — the formula uses absolute (kelvin) temperatures, which are always positive, so it computes correctly for −20 °C storage just as for refrigerated or room-temperature ranges, and it still weights the warmest (closest-to-thaw) excursions most heavily. Set the limit to your product's upper frozen ceiling (e.g. −15 °C for a −20 °C product) and enter the freezer history. Note two caveats: some products must never thaw-and-refreeze regardless of MKT (a hard rule), and ultra-cold products (−70 °C) have their own much lower limits — set them accordingly. As always, the product's labelled condition and stability data govern the disposition.

Because degradation is not linear with temperature — it accelerates roughly exponentially (Arrhenius). A simple average treats an hour at 30 °C the same as an hour at 20 °C either side of 25 °C, but the product is harmed far more by the hot hour. MKT weights each reading by exp(−ΔH/RT), so it reflects the true cumulative chemical stress. It is always ≥ the arithmetic mean, and it is the figure regulators expect for storage and distribution compliance.

Use a representative series with durations — typically the logger's interval readings, or summarised blocks of 'X hours at Y °C' if you only have an excursion summary. The more granular the data, the more accurate the MKT, but the result is dominated by the warm excursions, so capturing those accurately matters most. Don't average data before entering it — that defeats the point; enter the temperatures and let the calculator do the kinetic weighting.