Hands on Review: ThermoWorks Thermapen ONE!

Thermapen ONE Brisket

The Thermapen is a thermocouple thermometer produced by ETI, Ltd and sold by ThermoWorks. It’s used by restaurants, home cooks, homebrewers, grillers, bbq-ers and more.

Here’s an in depth hands on look at the latest iteration, the Thermapen ONE starting with a history of the Thermapen, accuracy and response time tests and lots more.

History of the Thermapen

The Thermapen was introduced in 1992. The original invention of the Thermapen was by Electronic Temperature Instruments Limited (ETI, Ltd.) of Worthing, England. Each subsequent version of the product has been engineered and manufactured by ETI, Ltd.

Thermapen was the first thermocouple thermometer designed for commercial and home kitchens. Prior to that time all other thermocouple thermometers were designed for science and industry; and were much larger, handheld devices with separate probes. These were generally priced at about $200 or more (after purchasing a probe).  Keep in mind that’s in pre-1992 dollars.

thermapen historyFrom left to right – Original Thermapen, Thermapen MK2, Super Fast Thermapen (now sold as Thermapen Classic), MK4, Thermapen ONE

Each model with some key innovations along with some notable events

Original Thermapen

  • Released in 1992
  • First Thermocouple food thermometer designed for consumer use
  • Available in white.
  • 7-8 second response time

Thermapen MK2 (Mark 2)

  • Released in 1996
  • New body design
  • Auto-on, no buttons
  • Available in gray until 1999 at which time a full range of colors was introduced
  • 7-8 second response time
  • The MK2 is awarded as Cook’s Illustrated’s “Best Thermometer” choice. A ranking every subsequent Thermapen has maintained.
  • Owen Instruments is incorporated and changes its name to ThermoWorks.

Thermapen MK2 with Super Fast Probe Tip

  • In 2000 ThermoWorks reduced the tip diameter to speed up response times.
  • Response times went from 7-8 seconds to 3-4 seconds

Super-Fast Splash-Proof Thermapen

  • Released in 2009
  • The first we see any level of water resistance. The Super-Fast Thermapen was splash proof.
  • Personalization Features Added – Ability to display in C or F, display in 1/10th degree or whole degrees and ability to disable auto shut off function
  • The Super-Fast Thermapan was the first model to feature end user calibration
  • 2-3 second response time
  • This model is still available as of this writing, it’s called the Classic Super-Fast Thermapen

Thermapen MK4 (Mark 4)

  • Released in 2015
  • IP67 Waterproof Rating
  • Auto rotating display, ambidextrous use
  • Intelligent backlighting
  • Uses easy to source and long lasting AAA batteries.
  • Motion sensing sleep and wake modes
  • 2-3 second response time

Thermapen ONE

  • Released in 2021
  • Maintains improvements from previous versions – personalization, auto-rotating display, motion-sensing sleep and wake mode, waterproof to IP67, AAA batteries, NIST-traceable calibration certificate
  • Improved accuracy ± 0.5°F (± 0.3°C)
  • Brighter backlight
  • Extended 5 year warranty
  • 1 second response time

One-offs, limited edition colors and special editions

Through the years there have been one-offs, limited edition colors and special editions. These have included surface models, a backlit model (before this became a standard feature), air models, IR/thermocouple combo and the extremely accurate Reference Thermapen, which you’ll see later in this post.

This best way to check for current offerings is to check out the Thermapens page

Check Current Price, Models & Availability:

Let’s Be Friends!

BBQ/Grilling/Cooking reviews, deals, tips, new product announcements, recipes and more

Connect with BBQ Finds to Stay In the Loop!

Hands on Review Thermapen ONE

Front of the Thermapen ONE Box

Back of the box details features and specs

What comes in the box – Printed instructions. A guide to better food through the proper use and care of your Thermapen ONE. Certificate of Calibration. Temperature at Home – Thermal Tips and Secrets.

Certificate of Calibration with serial number redacted. This certifies that my thermometer has been “calibrated against laboratory standards which are traceable, via International Agreement to all major national standards, including NIST.”

A look at the front of the Thermapan ONE. Probe is on the left. Backlit LCD screen. That little dot is the light sensor.

From the Manual – Intelligent Backlight: When the Thermapen ONE is turned on, a light sensor (small round window located just to the right of the main display) continuously monitors ambient light levels. As it gets darker, the intelligent backlight comes on automatically to read the digits in any light condition. Covering the light sensor will also turn on the backlight except in well-lit areas. The backlight will remain on for a minimum of 10 seconds. If the instrument is displaying the low battery symbol, the backlight brightness will be reduced to prolong battery life.

Backlight in action

Back of the Thermapen ONE

Close up of the back. ThermoWorks Utah, USA 801-756-7705. Made in the UK by ETI for ThermoWorks. ONE second, Waterproof to IP67. Do not leave in oven. Clean with damp cloth or antibacterial wipe. Not dishwasher safe. NSF certification symbol. Probe Range: -58 to 572 F – 50 to 300 C.

A closer look at the battery door

The battery door is easily removeable with a standard screwdriver

Battery door removed. This shows the AAA battery along with configuration buttons. M = menu, S = set.  You can set Temperature Display Units, Display Resolution (1 degree or .1 degree), Screen Rotation and Auto-Off/Sleep Mode.

I really like that this uses an easy to find AAA battery. It also offers a much longer life as compared to button type batteries that previous Thermapen versions used.

The battery door.

You can see the auto-rotating display has rotated to show the temperature correctly oriented.

A closer look at the tip of the probe. This reduced tip diameter, which was introduced in 2000, is one of the keys to super fast response times.

When folded in, the probe fits nice in the body of the thermometer

For comparison, the Thermapen Mk4 is on the left, the Thermapen ONE is on the right. From the front, there is one indication that these are different. The Mk4’s batter door is at the bottom.

For comparison, the Thermapen Mk4 is on the left, the Thermpan ONE is on the right.

Menu Settings for Thermapen ONE

To access customization settings, remove the battery door. This shows the AAA battery along with configuration buttons. M = menu, S = set.  You can set Temperature Display Units, Display Resolution (1 degree or .1 degree), Screen Rotation and Auto-Off/Sleep Mode.

Menu options for Thermapen ONE

Thermapen ONE Accuracy Tests

The setup. A stockpot of water heated to 170 deg F with an Anova Sous Vide Cooker. The Thermapen ONE on the left and a Reference Thermapen on the right. The sous vide heat stick has a built in pump that is constantly recirculating water. That helps to keep a consistent temperature. Note: I don’t recommend subjecting your Thermapen to constant heat/steam like this. I’m putting mine on the line for testing purposes.

The Reference Thermapen is a more accurate Thermapen (±0.1°F vs ±0.5°F for the Thermapen ONE) that’s usually used by labs. I do not recommend buying a Reference Thermapen, unless… you run a lab or otherwise have thermometers you need to check for accuracy. They have a higher accuracy and higher resolution (1/100ths of a degree). But they’re expensive and there’s a speed trade off. 20 seconds vs 1 second. All that to say, I use this tool because I periodically review thermometers. It’s not meant for every day use.

Although the Anova is set to 170 deg F, It’s not always going to be exactly 170 deg F. These are really good at holding a temperature, but not perfect. They’re going to kick on and off trying to keep things dialed in. The important thing for these tests is that the temperature is consistent throughout the stockpot.

Accuracy test with Thermapen ONE is full digit display mode

Accuracy test with Thermapen ONE is 1/10th digit display mode

A point in time snapshot. Thermapen ONE (full digit display mode) reading 127. Reference Thermapen reading 127.01.

A point in time snapshot. Thermapen ONE (1/10th digit display mode) reading 169.4. Reference Thermapen reading 169.40.

The Thermapen ONE is extremely accurate. At times it matched the Reference Thermapen exactly. At times it was within small fractions of a degree, always well within the stated accuracy specification. I want to say this is the most accurate thermometer on the market for non-lab consumer and commercial use, but I can’t really say that, because I don’t have every thermometer. What I can say is that my Thermapen ONE is extremely accurate and well suited to my needs in the kitchen, when BBQ-ing and more.

IP67 Waterproof Rating

Note: I don’t recommend purposefully subjecting your Thermapen to complete immersion. I’m putting mine on the line for testing purposes.

IP = Ingress Protection. IP ratings are a way to rate a devices resistance to dust and water. The first number shows dust protection the second number shows water protection.

For the first number/dust resistance, valid ratings are from 0, no protection at all to 6, completely protected from dust.

For the second number/water resistance, valid ratings are form 0, no protection at all to 8, protected against long term immersion under pressure.

The Thermapen ONE has a IP rating of 67

  • 6 = completely protected from dust
  • 7 = protected against the effects of temporary immersion in 15 cm to 1 meter of water for up to 30 minutes

So the Thermapen ONE has complete protection from dust and excellent protection from water. It is not dishwasher safe. That would be more like an IP68 rating.

Response Time Testing

Back when I first started doing thermometer reviews, response time testing was fairly easy. I would usually take a video and use video timestamps to determine response times. That’s when when thermometers had 7 to 8 second response times or even 2 to 3 second response times. A response time of one second is tough to measure.

This video shows me dropping the thermometer into the hot water bath I used for accuracy testing. It’s not a numerical measurement, but it will give you a great idea of just how fast the Thermapen ONE reacts.

Using the Thermapen ONE!…

Home Brewing

The Thermapen ONE is at home in the kitchen, back yard and more!  Making your own beer is easy and rewarding. Need help? Check out my homebrewing site homebrewfinds.com or.. I will personally answer any questions you have about brewing – contact me – or I’ll do my best to direct you to a resource that can help. More homebrewing related pictures below.

Thick Pork Chops

These chops were a good inch or inch and a half thick

After the flip

Checking temperatures with my Thermapen ONE

For this cook, I used my Recteq RT-B380 “Bullseye” It does a wonderful job producing high heats with a max setting of 749 deg F

Steak Cook

Reverse Sear Ribeye

What is Reverse Searing?

I would say the standard way to cook a steak, chop or similar is to cook on high heat to sear the meat then, if necessary, apply indirect heat to finish off the meat.

With a reverse sear, the order is… reversed. Low temperature is applied first to add smoke flavor and then high heat is applied at the end to sear the meat. This allows the meat to absorb flavors that would otherwise, overcook or dry out the meat if done in the standard way.

In order to withstand the reverse searing process, I recommend a larger piece of meat. If you have a thin steak, it’s going to cook too quickly.

For seasoning, my standard for steak is… salt, pepper and garlic powder on one side and Montreal Steak Seasoning on the other.

Checking temp using the Thermapen ONE during the smoke portion of the cook.

Smoking is done, now on high heat. This was done on my Recteq Bullseye.

Finished product!

Smoked Brisket

Thermapen ONE Brisket

See: My Process for Smoked Brisket and Burnt Ends for a rundown of my brisket procedure

Thermapen ONE Specifications

  • Range: -58.0 to 572.0°F (-49.9 to 299.9°C)
  • Accuracy: ±0.5°F (±0.3°C) from -4 to 248°F (-20 to 120°C) otherwise ±1.8°F (±1.0°C)
  • Resolution: Factory set to 1° (user reconfigurable to 0.1°)
  • Response: Time Full reading in 1 second (0.2 seconds time constant)*
  • Probe: 4.3 L inches x 0.12″ dia. (reduces to 0.06″ dia.), High Performance Type K Thermocouple
  • Display: 1 H x 1.54 W inches (25 H x 39 W mm) LCD, rotates 360°, Intelligent Backlight
  • Sleep Mode: 10 to 180 seconds, user selectable (user reconfigurable to disable)
  • Water Resistance: IP67
  • Operating Range: –4 to 122°F (–20 to 50°C), max ambient limits of Thermapen body
  • Battery: 1.5 volt AAA, 2,000 hours typical (without backlight)
  • Dimensions: 6.1 W x 1.7 H x 0.74 D inches (156 W x 48 H x 19 D mm)
  • Weight: 0.25 lbs (115g)
  • Warranty: 5 years
  • Certificate: Includes NIST-traceable calibration certificate


In my experience as a home cooking enthusiast, homebrewer and BBQ-er I’ve used lots of thermometers. Lots. I’ve performed in depth reviews on a number of those. I got my first Thermapen in 2013 and I haven’t looked back. Each release has built on previous generations.

This is an extremely high quality tool that makes tasks around the kitchen, grill and more easier. It’s very well made, lightning quick and extremely accurate. Just a pleasure to use.

After extensively using the Thermapen ONE I can confidently recommend it to you.

Check Current Price & Availability:

Thermapen ONE Manual

Thermapen ONE Operating Instructions – check product page for current version

More Photos

Checking Beer Serving Temp

Checking beer pH sample temp

Checking beer mash temp

More about homebrewing….

Making your own beer is easy and rewarding. Need help? Check out my homebrewing site homebrewfinds.com or.. I will personally answer any questions you have about brewing – contact me – or I’ll do my best to direct you to a resource that can help. More homebrewing related pictures below.

My BBQ Rub Recipe

Connect with BBQ Finds to Stay In the Loop!

Also: Our Fuel Deals Roundup!

hardwood pellet and charcoal deals

Special thanks to ThermoWorks for providing the units used for evaluation in this review.

Thanks to Brad Probert for the homebrewing related photos. Check out Brad’s website – beersnobby.com

Price, promotions and availability can change quickly. Check the product page for current price, description and availability. top:tponervw tag:tpr

Leave a Reply

Your email address will not be published. Required fields are marked *