Thermoworks just announced their newest product, the Thermapen ONE this week. We've been huge fans of the Mk4 meat thermometer for quite some time, so we were particularly excited to learn how they improved on this great product.

And since we were so curious how these two generations of Thermoworks instant-read thermometers compared, we decided our followers might be as well.

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Thermapen One Performance

The Thermoworks Thermapen One provides internal temperature readings that are accurate to 0.5 f in one second. No other instant-read thermometer on the market performs that quickly or that accurately. Other thermometers take several seconds to read temperatures that may only be accurate to within 1-2 degrees if even that.

As with most instant-read thermometers available, the temperature range of the Thermoworks Thermapen One far surpasses any practical needs that one might have for getting internal temperature readings. I can't even imagine what one might test as cold as -58°F or as high as 572°F. Temperatures outside that range would usually be captured by utilizing an infrared thermometer rather than an instant-read thermometer.

Thermapen One meat thermometer

What is the difference between Thermapen ONE and Thermapen Mk4?

While the Thermoworks Thermapen ONE is very similar to its predecessor, there are several features that definitely set it apart.

Thermapen ONE

Thermapen Mk4

Thermoworks Thermapen One
Thermoworks Thermapen Mk4

Auto-rotating display

Auto-rotating display

Waterproof to IP67

Waterproof to IP67

Motion-sensing sleep and wake mode

Motion-sensing sleep and wake mode

Readings within 1 second 

Readings within 2-3 seconds

±0.5°F accuracy

±0.7°F accuracy

Temperature range -58°F to 572°F

Temperature range -58°F to 572°F

5 year warranty

2 year warranty

Brighter and more-responsive automatic backlight

Intelligent backlight

10 color options

Limited color options left

easier access to the user settings


Is the Thermapen Mk4 discontinued?

The Thermapen Mk4 was still available for many months following the release of the Thermapen One at a closeout price, however it is no longer in production and at this point in time the remaining inventory appears to be all gone. However, the Thermoworks Thermapen Classic is still available.

What makes a Thermapen different?

A Thermoworks Thermapen is different than most competitors because it uses a thermocouple sensor instead of a thermistor sensor. Brands using a thermistor sensor are using an actual temperature-sensitive resistor to measure temperature. The Thermapen uses a thermocouple sensor, which is essentially two wires of different alloys that are welded together. A thermocouple measures temperature at the "bead" where the two wires are welded together, and in the Thermapen that's in the very tip at the end of the folding probe.

Temperature itself is very difficult to measure, so we as humans have created ways to determine the temperature based on how it affects other things. When the two wires of a thermocouple are welded together, it generates a voltage and that voltage changes based on the temperature of the welded junction. When the voltage in the junction changes, the electronics of the Thermapen translate that to temperature, which is, in turn, faster to read than a thermistor. 

While we're getting all geeky here and talking about what makes a Thermoworks Thermapen different, let's talk about the location of the sensor. Not all instant-read thermometers place their sensor in the absolute tip of the stainless steel probe. It's mind-boggling to be sure, but when you don't know where the sensor is, you're left to guess where you're actually measuring temperature. It could be 1 inch from the probe tip or even higher, so when you think you've found the thermal center of a piece of meat, with a Thermapen, you can have confidence you're getting a measurement where you intended to.

lcd screen of the Thermapen One showing temperature reading

What We Loved About the Thermapen ONE

Speed and Accuracy

The Thermoworks Thermapen One boasts industry-leading speed and accuracy to 0.5° F. When testing the internal temperature of a steak cooking over a hot grill, time is of the essence and I want to achieve accurate temperature readings as fast as possible to avoid burning my hand. And in the case of cooking a steak to your preferred level of doneness, having an accurate thermometer that is within half a degree will keep your medium-rare steak from creeping too far over to the medium range. Previous models of Thermapen were nearly as accurate (±0.7°F) but with a longer response time than the Thermapen One.

Auto-Rotating Display

This particular feature appears to function in exactly the same way as in the Mk4. I absolutely love that no matter what way I'm holding it, the LCD screen display is easy for me to see a temperature reading without craning my neck. If for some reason you don't appreciate this feature as much as I do, you can change the settings to lock in your preferred display orientation. My wife and I are both right-handed, but I would imagine this feature would be especially appreciated by our left-handed friends who are used to being forced to read temperatures upside down on other cheap thermometers.

360° rotating display
360° rotating display
360° rotating display
360° rotating display

Intelligent Backlight

In this new version of the Thermoworks Thermapen, the backlight is even brighter than the Mk4 and is slightly more responsive as well. Since I'm usually grilling in low light through most of the winter, I absolutely love this feature on my instant read thermometer.

backlight comparison of Thermoworks Thermapen ONE and Mk4 in low light

User Settings Access

I'll be honest, I don't require access to the user settings often. But I like to know I can get to them easily should I suddenly feel the need to measure temperature to the tenth of a degree. The settings and battery compartment on the Thermapen ONE are way easier to access than the Mk4.

Battery compartment of Thermoworks Thermapen One

Battery Life

The Thermoworks Thermapen One has a 2000 hour battery life using a single AAA battery. The motion-sensing sleep and awake mode significantly helps to conserve battery life by intuitively turning it off when not in use. And eventually, when the day comes when you do actually need to change the battery, the newly designed battery compartment is super easy to access.

Calibration Certified

Each Thermoworks Thermapen One comes with a NIST traceable calibration certificate. What does that even mean? It certifies that Thermoworks is equipped and able to calibrate their equipment to the National Institute of Standards and Technology (NIST) standards and therefore the products they sell match those same measurement standards. This NIST traceable calibration certificate is something that most other thermometer brands cannot and do not offer.

5 Year Warranty

Nothing says a company stands behind their product more than extending the life of their warranty. This speaks volumes to the quality that Thermoworks puts into this product.

Who is the Thermoworks Thermapen One for?

The Thermoworks Thermapen One is a favorite of anyone who uses instant-read thermometers for internal temperature readings. Professional chefs and home cooks alike, anyone who values food safety would be impressed by the speed and accuracy that comes with this model over other thermometers on the market. In applications where accurate measurement is critical such as food processing plants and candy making, there is no better food thermometer than the Thermoworks Thermapen One.

Final Thoughts on the Thermapen ONE

instant read thermometer ice water test

I didn’t think the Thermoworks Thermapen could get any better but they actually managed to achieve it! I wouldn't say there were any mind-blowing changes; it is still very similar to the Mk4 and even the Thermapen classic. However, it is clearly the more advanced version of this instant-read thermometer.

The Thermoworks Thermapen ONE is honestly the best instant-read thermometer we've tested to date. So if you like to have the best of the best, look no further and order ONE for yourself.