What is mean kinetic temperature?
Mean kinetic temperature (MKT) is a single temperature that has the same effect on a product as the whole series of temperatures it actually met. Heat speeds up chemical change faster than cold slows it, so a warm hour counts for more than a cold hour. That is why MKT sits above the plain average whenever the temperature varies.
Paste a log of readings, or list the hours spent at each temperature. The calculator gives the MKT, the lowest, highest and mean temperature, the time outside your range, each period outside it, and a chart.
The formula is the one Haynes published in 1971 and pharmacopoeial storage guidance describes, for example USP general chapter <1079.2>. Check the current edition of the chapter that applies to your product.
| Series | Readings (°C) | Mean | MKT |
|---|---|---|---|
| Steady | 5 / 5 / 5 / 5 | 5.0 °C | 5.00 °C |
| Half cold, half warm | 1 / 1 / 9 / 9 | 5.0 °C | 5.94 °C |
| One warm spike | 3 / 3 / 3 / 11 | 5.0 °C | 5.83 °C |
All three series have a mean of 5.0 °C. Only the steady one has an MKT of 5.0 °C. The others rise because the warm readings count more. ΔH/R is 10,000 K.
What inputs do you need?
| Input | Where to find it | Tip |
|---|---|---|
| Readings | The temperature log from a logger or from a tracker with a temperature probe | In °C, at a fixed interval, complete from loading to delivery. |
| Timestamps (optional) | The date and time column in the exported log, as YYYY-MM-DD HH:MM | They let the tool find gaps and measure the real spacing. |
| ΔH/R | Your quality system or the product data. The default is 10,000 K | A typical value. Write down the one you used. |
| Allowed range | The product label or your own specification | Leave it empty to skip the range checks. |
| Hours at each temperature | The trip schedule or the storage stages | For the second tab, when you have no complete log. |
ΔH/R = 10,000 K (typical), the range 2 to 8 °C (example) and the 30-minute interval (example) are placeholders. Use your own product data. Readings must be in °C.
How is MKT calculated?
The formula
The result is converted back to °C. With a steady temperature, MKT equals that temperature. With hours at each temperature, each term is multiplied by its hours and divided by the total hours.
Time outside the range
Source for the formula: Haynes JD. Worldwide virtual temperatures for product stability testing. J Pharm Sci 1971;60(6):927-929. Source for the pharmacopoeial guidance: the current edition of USP <1079.2>. The citation was checked on PubMed (PMID 5128949) and the chapter title on doi.usp.org on 3 Nov 2026. The chapter text is sold by subscription, so check the ΔH/R value in the edition you use.
Worked example: a 24-hour chilled route
The default readings are 48 example values, one every 30 minutes from 06:00, with a door-open spike of two hours around 21:00. The range is 2 to 8 °C and ΔH/R is 10,000 K.
- Lowest 3.5 °C, highest 10.4 °C, arithmetic mean 4.85 °C.
- MKT is 5.03 °C, 0.18 °C above the mean, and inside the 2 to 8 °C range.
- 4 readings are outside the range, a single period of 2 hours. The verdict is therefore "MKT in range, readings outside".
- Second tab: 18 hours in four stages. The cold store (4 °C, 10 h) and the cooled transport (5.5 °C, 6 h) are in range. The dock (14 °C, 0.5 h) and the wait at delivery (22 °C, 1.5 h) are not.
- The weighted mean is 6.28 °C, but the MKT is 8.64 °C, outside the range, because the 1.5 hours at 22 °C count heavily. 2 hours are outside the range.
How do you read the results?
- MKT against the mean: the gap shows how much the warm readings matter. A large gap means the series swings, even if the mean looks fine.
- MKT against your range: the first check. Outside the range is a stop for review. Inside the range does not mean every reading was fine.
- Readings and time outside the range: the second check. A short spike and a long drift can give the same MKT and need different follow-up.
- Periods outside the range: start with the longest and the highest. Look at what the vehicle was doing at that time.
- MKT at other ΔH/R: a quick view of how much the constant matters for your series.
Assumptions and limits
MKT assumes readings at equal spacing, so gaps and uneven logging change the answer. It works in °C only: convert °F with (°F − 32) × 5 ÷ 9 first. A single MKT figure hides a spike, so always read the highest reading and the time outside the range too. ΔH/R is a typical default, not a value for your product, and the range is your own input. MKT is a screening figure for review: it does not say whether a product can be used, and it is not an approval or a compliance result. Nothing you enter leaves your browser until you ask for the report.