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Polar RS300X Heart Rate Monitor

by Polar
3.3 out of 5 stars  See all reviews (37 customer reviews)

RRP: £121.50
Price: £81.06 & FREE Delivery in the UK. Details
You Save: £40.44 (33%)
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Colour Name: Black
In stock.
Dispatched from and sold by Amazon. Gift-wrap available.
  • Automatic age-based target zone - bpm / %
  • Average and maximum heart rate of each lap
  • Polar Fitness Test
  • Polar OwnCal® - calorie expenditure
  • Polar OwnCode® (5kHz) - coded transmission
  • Polar OwnZone® - personal heart rate zone
  • Polar sport zones
  • Training files (with summaries) - 16
  • Graphical target zone indicator
  • HeartTouch - button-free operation of wrist unit
  • Interval trainer guided workouts - heart rate / pace / distance
  • ZoneLock
  • ZonePointer
  • StopWatch
  • Time of day (12/24h) with alarm and snooze
  • Weight: 41g

Frequently Bought Together

Polar RS300X Black Heart Rate Monitor + Polar Bike Mount Set  HRM Accessory - Black
Price For Both: £88.41

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Colour Name: Black

Product details

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  • ASIN: B001NGP0MI
  • Date first available at Amazon.co.uk: 17 April 2009
  • Average Customer Review: 3.3 out of 5 stars  See all reviews (37 customer reviews)
  • Amazon Bestsellers Rank: 7,310 in Sports & Outdoors (See Top 100 in Sports & Outdoors)
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Product Description

Manufacturer's Description

Body measurement features:

Automatic age-based target zone – bpm / %

To help you train safely and effectively, the training computer determines your heart rate target zone limits automatically according to your age-based maximum heart rate (220 minus age). The limits are determined either in beats per minute (bpm), as a percentage (%) of your maximum heart rate, or as a heart rate reserve (% HRR). See also Maximal oxygen uptake (VO2max) and Manual target zone.

Heart rate – bpm / %

Heart rate is the measurement of the work your heart does. Heart rate can be expressed as the number of beats per minute or as percentage of your maximum heart rate. Heart rate can also be expressed as a percentage of your heart rate reserve, meaning the difference between your resting heart rate and maximum heart rate (HRR = HRmax - HRrest). In Polar software or during strength training, heart rate can be displayed as a graphical trend.

HR-based target zones with visual and audible alarm

You can define your target zones for a training session based on heart rate to help define the right intensity. When you are out of the preset zones, the training computer will give a visual and audible alarm.

HRmax (age-based)

The highest number of heart beats per minute (bpm) during maximum physical exertion. For a rough estimate of your maximum heart rate, subtract your age from 220. HRmax is a useful tool for determining the intensity of training as intensity zones can be defined using HRmax. Some Polar products define maximum heart rate during the Polar Fitness Test, see also HRmax (Polar Fitness Test -based).

HRmax (Polar Fitness test-based)

Some Polar products predict your HRmax simultaneously with the Polar Fitness Test. This predicted HRmax value is more accurate than the age-based formula (220 minus age).

Manual target zone – bpm / %

This feature enables you to define the target zone as you want and is suitable for your training. You can set the target zone for your training as beats per minute (bpm), as a percentage of your maximum heart rate, or as a percentage of your heart rate reserve (HRR%).

Polar Fitness Test

Polar Fitness Test measures your aerobic fitness at rest in just five minutes. The result, Polar OwnIndex, evaluates your maximal oxygen uptake (VO2max). With the Polar Fitness Test you can measure your aerobic fitness by yourself, automatically and without any exertion. All you need is your training computer. The Polar Fitness Test is as accurate in predicting the VO2max as any sub maximal fitness test. The test is based on heart rate and heart rate variability at rest and personal information.

Polar OwnCal® – calorie expenditure

Polar OwnCal calculates the number of kilocalories expended during training. This feature allows you to follow the kilocalories expended during one training session and cumulative kilocalories expended during several training sessions. Some Polar products also estimate the fat-burning percentage (fat% on display), that is, kilocalories expended from fat during a workout which is expressed as a percentage of the total kilocalories burned.

Polar OwnCode® (5kHz) – coded transmission

Coded heart rate transmission automatically locks in a code to transmit your heart rate to the training computer. The training computer picks up your heart rate from your transmitter only. Coding prevents interference from other training computers.

Polar OwnZone® – personal heart rate zone

Polar OwnZone® determines your personal heart rate limits for a training session. Depending on the day and time, your physical state may vary, for instance, if you are stressed or tired, or if you are not fully recovered from your latest training session, Polar can determine that information from your heart rate and guide you to your ideal training zone for that moment.

Polar sport zones

Polar sport zones provide an easy way to select and monitor the intensity of your training and to follow sport zones based training programs. Training is divided into five zones based on percentages of your maximum heart rate: very light (50-60%HRmax), light (60-70%HRmax), moderate (70-80%HRmax), hard (80-90%HRmax) and maximum (90-100%HRmax).

Recording features:


Totals includes your training data starting from the last reset enabling you to follow your long-term training.

Weekly history

Weekly history gathers your weekly training data. By selecting a week, you can review your training data for the week.

Training features:

Automatic lap recording

With this feature you can set your training computer to take laps based on preset distance, for example, every 1 km/mi.

Display zoom

Display zoom feature allows you to zoom in information on the display during training.

Graphical target zone indicator

This feature points out graphically on the display the zone you are in during a training session helping you to stay on the desired intensity zone.

HeartTouch – button-free operation of wrist unit

When HeartTouch is on, different training information during training can be accessed without pressing buttons, for instance, when gloves make pressing buttons difficult, by bringing your training computer close to your transmitter.

Interval trainer guided workouts – heart rate / pace / distance

Create interval guided workouts based on time, heart rate, speed/pace or distance guidance with up to three linked timers or distances and up to three target zones.

Time and distance based interval timers

Use timers, for example, as a training tool in interval training to tell you when to switch from a harder to a lighter period and vice versa. The timers can be time- or distance- based.

User configurable displays – two lines

This feature allows you to configure training computer displays to show the information that you need during your training session. Configure the displays either in the training computer or in ProTrainer 5 software.


ZoneLock feature helps you to accumulate certain intensity. You can either lock a zone before a training session or during it by pressing a button when you are on the desired zone.


ZonePointer is a visible and moving symbol on the training computer display indicating whether you are inside the pre-set target zone. This feature helps you to reach the desired intensity/pace/speed/cadence targets.

Watch features:

  • Backlight
  • Date and weekday indicator
  • Display text in English, German, French, and Spanish
  • KeyLock
  • StopWatch
  • Time of day (12/24h) with alarm and snooze
  • Water resistant – 50m
  • Product Description

    The Polar RS300X is the perfect training partner. Without knowing your heart rate, you can only get so far. The RS300X combines these three to give you a true understanding of the effort you put in to your workouts.

    Customer Questions & Answers

    Customer Reviews

    Most Helpful Customer Reviews
    15 of 17 people found the following review helpful
    4.0 out of 5 stars Heart rate monitor 24 Dec 2010
    Colour Name:Orange
    I have been using this monitor for nearly a year now and I am quite happy with it. I use it for spinning lessons and when I am out training. The fitness test is quite useful as well as the training diary. Even after a year of use the watch still looks like new and is wearing well.
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    15 of 17 people found the following review helpful
    1.0 out of 5 stars Dissapointed! 30 Aug 2011
    By Seanhay
    Strap has broken within 18 months of purchase. As the watch is built in such a way that the strap can't be replace the watch is now useless!
    Built in redundancy??
    Was this review helpful to you?
    33 of 39 people found the following review helpful
    5.0 out of 5 stars Essential Purchase For Anyone Looking to Get Fit 24 Nov 2009
    Colour Name:Orange
    Having been training regularly for little over a year I felt I needed something to kickstart my regime again, as I felt I'd plateau'd. I kept reading people's suggestions online and in various magazines about heart rate monitors but never felt I'd need one as, though I want to get fit, it's hardly a pressing priority in my life. I exercise as regularly as I can and that's enough for me. But I'd noticed my time in the gym wasn't proving as effective and I felt to some extent a little disheartened when spending a lot of time training and not reaping the benefits. So I needed a new decent sports watch and looking on Amazin found this Polar RS300X for slightly more than I wanted to pay, but given it's heart rate monitor, a bargain price.

    I've had this now for four weeks and can honestly say its totally reinvigorated my training. what's more, due to the set-up I have I now train faster and harder in the time allotted. So my training has improved, I'm back on track and I'm actually spending less time doing weights, as I'm well aware that I need to try to keep my heart rate round my specific target. No time for slacking off, so it helps keep pushing me on.

    The heart rate monitor is an essential tool in training, be it for professionals or amateurs. This one is the first I've owned and I love it, plus its a funky orange colour! Great watch, great training device with tons of functions. Excellent value. I can't recommend it enough.
    Was this review helpful to you?
    1 of 1 people found the following review helpful
    5.0 out of 5 stars Excellent functionality 17 Jan 2013
    By Jimbo M
    Colour Name:Black|Verified Purchase
    Very pleased with this HRM. I had a more basic one but the additional information that is captured and broken down is very helpful. Whereas I used to note my heart rate but fairly well ignored it in terms of adjusting my pace. With this Polar RS300X I have run much more to the pace I should.

    The HRM reads the heart rate very reliably and accurately. I don't have the GPS or footpod attachments but using the Endomondo app with my mobile provides all the information I need.

    I have found the fitness test useful in setting a benchmark and will be interested to monitor improvements over time.

    I did wonder whether the £20 more than a simple model was worth spending. I think that the additional functionality did make this a good investment for me. Whether it is better value for you, you will need to judge.

    Overalll, highly recommended.
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    1 of 1 people found the following review helpful
    4.0 out of 5 stars HRM 7 Feb 2010
    Colour Name:Black
    This HRM does what it says on the tin. I wear it all the time as it is a good regular watch, not too bulky or ugly, as it is a HRM. I use it just with the chest strap, but I like the fact I have the option to buy other accessories to enhance it's performance, footpod etc.
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    5 of 6 people found the following review helpful
    5.0 out of 5 stars good product 1 Dec 2009
    Colour Name:Black
    Easy to use product good and would recomend if you are thinking of buying a heart fitness monitor
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    17 of 22 people found the following review helpful
    1.0 out of 5 stars Disappointing performance for the money spent 27 May 2010
    I wanted to write this review to express my dissatifaction with the Polar RS300X with G1 GPS sensor. I have purchased Polar products twice before and was very happy with the products until I purchased this one.
    To Begin with, the telemetry strap works intermittently. While the strap will work for five to six days, when it stops working it I have reapplied water to the sensors, detached and reattached the transmitter, stopped and restarted the exercise monitoring program on the wrist watch, readjusted the strap, checked to make sure the battery cover is still closed, and still was not able to get a heart rate signal. It is not until after 20-30 minutes of leaving the watch program on that I exit the program and then restart it and it actually starts working, but I am usually done with my work out.
    Lastly, the GPS sensor is the most aggrivating piece of equipment I have ever used. There is only one button to operate it and having consulted the onstructions several times I am still unable to get it to start working after the first button press. In fact, I end up pressing the button ~ten times just to get the red light to blink once, then another ~ten times before it starts blinking steadily looking for satellites. It has taken anywhere from a minute to as much as ten minutes to get a GPS signal. Usually it works fine afterwards, but today when I finished my run it had switched itself off.
    To be fair, the watch works excelellently and the USB link works flawlessly so no complaints there.
    Read more ›
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    10 of 13 people found the following review helpful
    2.0 out of 5 stars Disappointing performance of HRM 31 Aug 2010
    I bought this watch to replace a more basic HRM which did not have a lap counter (which I wanted for interval training). I chose it because of the reputation of the Polar brand and the various training functions offered by the watch.
    However, the performance of the HRM has been erratic. Problems include: taking several minutes to find a signal; giving wild heart rate readings (frequently in the 200s, well above my Maximum HR, when the correct HR is around 110); freezing on a particular HR and not displaying changes in the HR in response to different exercise intensity. I have been careful to ensure the transmitter electrodes are wet, and have tried changing the battery in the transmitter, but neither have helped. Unfortunately, training with an unreliable HRM is worse than training with none, since it means that I can't trust any reading it gives me without double-checking by taking a manual pulse reading. Very disappointing given the relatively high price of this product.
    Was this review helpful to you?
    Most Recent Customer Reviews
    5.0 out of 5 stars Five Stars
    husband loves it. delivered the next day!
    Published 1 month ago by Caroline Perry
    1.0 out of 5 stars No GPS!
    Only reason why I got is bc its display shows distance and speed. But it actually comes without GPS! Spend a bit more on one of the Garmin pieces and dont bother with this!
    Published 4 months ago by Ivan
    5.0 out of 5 stars General Exercise
    I run albeit a little slower than in my youth and do endurance cycling. The watch function ability is exactly as I thought it would be and suits me fine. Read more
    Published 4 months ago by Richard Williams
    1.0 out of 5 stars Poor piece of technology
    I've owned two of this model and they have both performed poorly. Finishing a workout with a fully recorded, accurate log is a rare occurence. Maybe 1 out of 5. Read more
    Published 5 months ago by Bartleby
    1.0 out of 5 stars Polar RS300X HRM
    I do not usually write product reviews but made an exception for this item as it is so disappointing for the price of the best part of £90. Read more
    Published 6 months ago by C Johnson
    2.0 out of 5 stars Not for me
    Too complicated and did not do everything I wanted. Sold it after two weeks fiddling about. I have found my Garmin to be much better.
    Published 8 months ago by garry douglas
    2.0 out of 5 stars Uses batteries and isn't very accurate.
    This product worked fine to start with but then the battery in the transmitter unit would run down after only two months use (used three times a week at an hour per time). Read more
    Published 11 months ago by Paul Stariski
    5.0 out of 5 stars basic functions but does everything well
    good watch. same buttons for similar functions as my previous Polar HRM. Better chest strap than the old model. Easy to set up and get started!
    Published 12 months ago by A W Mathers
    5.0 out of 5 stars quality and price spot on
    you can't go wrong with polar, I have tried others but the ease and functionality as well as the polar quality is above the price asked for by this seller, would recommend using... Read more
    Published 15 months ago by gary
    5.0 out of 5 stars A heart beat away
    Quick delivery and just as expected. It is a Polar heart monitor. What more can I say? It was a good price for the functions and fror what I want to use it for.
    Published 17 months ago by Andrew David Teare
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