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Updated July 2026 · real, multi-region App Store reviews
Head-to-head

Instant Heart Rate vs Cardiio

Instant Heart Rate 4.9★ · Free + IAP 70
Winner Instant Heart Rate
Cardiio 4.7★ · Free + IAP 55

Instant Heart Rate is generally more accurate and offers a better user experience for basic heart rate monitoring, despite issues with its subscription model, while Cardiio struggles with consistent readings and customer support.

Full reviews: Instant Heart Rate · Cardiio

Instant Heart Rate (App A) generally provides more accurate heart rate readings and a simpler user experience for basic monitoring, though many users report issues with its subscription practices and recent updates. Cardiio (App B) is also easy to use but frequently fails to get readings due to 'poor signal quality' and has unresponsive customer support.

Head to head

Accuracy edge: Instant Heart RateR5R7R8R14
Instant Heart Rate Many users find Instant Heart Rate to be accurate, with some comparing it favorably to manual checks or other devices R5R8R14. However, a significant number of recent reviews report it as inaccurate, sometimes giving excessively high or inconsistent readings R7R15.
Cardiio Cardiio's accuracy is a mixed bag; some users find it helpful for monitoring their heart rate , but others report it as inaccurate, giving readings 'all over the place' .
Ease of Use & Reliability tieR3R9R12R15
Instant Heart Rate Instant Heart Rate is praised for being simple, quick, and easy to use R9. However, many users experience issues with the camera not turning on, the app failing to detect a finger, or readings taking too long or freezing R3R12R19R39. Recent updates have also caused problems like not reading low heart rates or losing past readings R9R15R24.
Cardiio Cardiio is also noted for being simple and easy to check heart rate anywhere . However, a major recurring issue is the app frequently failing to get a reading, often citing 'poor signal quality' even when users believe the signal is good . This problem seems exacerbated on newer iPhone models due to camera/flash positioning .
Features tieR15R21R24R34
Instant Heart Rate Instant Heart Rate offers basic heart rate monitoring, with the free version generating a plethysmogram and detecting arrhythmias . Premium features include heart age R21 and the ability to store and track readings, though some users report issues with data retention and sharing R15R24. Some users mistakenly expect blood pressure monitoring, which the app does not provide R34R37.
Cardiio Cardiio also provides heart rate monitoring and can warn users if their heart rate is too low or high . Some users appreciate its ability to confirm irregular rhythms like A-fib . Like App A, it does not offer blood pressure monitoring R65. There are reports of bugs with features like the endurance score and the insights tab .
Price/Value & Subscription Issues tieR1R4R6R7
Instant Heart Rate Instant Heart Rate is advertised as Free + IAP, but many users report being immediately charged for annual subscriptions (around $60-64) after starting a 'free trial' or being unable to cancel subscriptions R1R4R6R7. The free version has become very limited, sometimes only allowing 7 seconds of measurement, making it 'pretty useless' .
Cardiio Cardiio is also Free + IAP, but similar to App A, many users report being charged immediately after signing up for a 'free trial' or being billed without consent . Some users find the free version useful for approximate heart rate, but don't see value in the pro version given the reading inconsistencies .
Support & Privacy tieR4R6R10R13
Instant Heart Rate Instant Heart Rate receives strong criticism for its customer service, with users reporting difficulty canceling accounts, being charged despite cancellation, and unhelpful responses regarding refunds R4R6. Many users are concerned about privacy, citing the requirement to create an account and potential data selling R10R13.
Cardiio Cardiio users also report unresponsive customer support, with requests for help going unanswered, especially regarding stopping reminders or canceling accounts . There are also reports of the FAQ section defaulting to a gambling site, raising security concerns .
Pick Instant Heart Rate if

you need a quick and simple heart rate check and are willing to navigate potential subscription pitfalls, or if you find other apps less accurate R14.

Pick Cardiio if

you are looking for an app to help monitor specific heart conditions like A-fib and find its warnings useful, and are not deterred by potential signal quality issues .

Evidence note: Both apps have a significant number of negative reviews related to deceptive free trials and subscription charges, making it difficult to assess their value proposition solely on features. The reliability of readings is a common complaint for both, particularly on newer iPhone models for Cardiio.

Frequently asked

Is Instant Heart Rate truly free?
Instant Heart Rate is advertised as Free + In-App Purchases, but many users report being immediately charged for an annual subscription, often around $60-64, after starting a 'free trial' or finding the free version too limited to be useful R1R4R7R28.
Do these apps measure blood pressure?
Neither Instant Heart Rate nor Cardiio measure blood pressure; they only take pulse readings, and users expecting blood pressure monitoring will be disappointed R34R37R65.
Why do these apps get 'poor signal quality' errors?
Users of Cardiio frequently report 'poor signal quality' errors, often due to difficulty placing a finger correctly over the camera and flash, especially on newer iPhone models where the lenses are spaced further apart . Instant Heart Rate also has issues with the camera not detecting a finger or freezing during readings R12R19R39R58.

What reviewers actually said

Built only from these 120 real reviews (foreign ones translated). Superscripts jump to the quote here. Apple has no per-review links, so [ref] opens that app's reviews on the App Store.

  1. [R5] Instant Heart Rate 5/5 · US I think this is pretty accurate: I’ve been feeling weak and dizzy due to my heart rate going up. This helps me know when my heart is going above 100 bpm and when I need to lay down.
  2. [R7] Instant Heart Rate 1/5 · US Be Aware this App isn’t Accurate, Don’t Waste Your Money!: This app is fine if you’re using the free version. It’s not accurate, which is why purchasing any paid subscription is not worth it. Save your money and find a different app that can actually detect your heart rate. I accidentally paid for a year long subscription for $60 when I thought I’d try out the paid version for a free 3 day trial,
  3. [R8] Instant Heart Rate 5/5 · US Its okay I guess: The app is nice, helpful but is it really true? Either way..it has really helped me a lot in the past month and days too and pretty good anyway over all it seems pretty accurate oh and by the way can you add a iPad version please and thank you?
  4. [R14] Instant Heart Rate 5/5 · US Most accurate!: I downloaded three apps and one said my bpm was 53, one said 72, and this one said 117. I checked my bpm manually and I got 116.
  5. [R3] Instant Heart Rate 3/5 · US Maddening to sign in: There was no way to close the keyboard so I could reach the "sign up" or "login" options at the top. I had to force quit the app and start over multiple times to get signed in. I already had an account from a long time ago, so I used the forgotten password feature. In the email, there was a button to open the app, but it took me to the web instead. It took forever to take
  6. [R9] Instant Heart Rate 3/5 · US Works well, won’t read low HR: App is easy to use and works well. Only problem is, since the new update, it won’t work for a heart rate less than 40 bpm. Sometimes my heart rate can be 38-39. If this is true (per my watch), the app glitches and won’t register it. It just doesn’t work!!! This didn’t used to be true, only since a recent update. Very annoying!!
  7. [R12] Instant Heart Rate 3/5 · US Great app when the Camera works: Half the time the camera won’t turn on on my IPhone. Meaning I cannot use the app properly. It’s a 50/50 shot whether or not it works for me.
  8. [R15] Instant Heart Rate 3/5 · US Could be more useful: The info it collects is helpful, except it only retains part of the data collected from each test. It would be far more useful for me if the whole chart was stored and shareable the same way it’s collected. Also, if I use it 3X in a row, sitting in the same chair, same position, I get 3 very different measurements. Not sure why. So it’s not very useful for me now. If I knew
  9. [R21] Instant Heart Rate 3/5 · US What gives?: I am a premium member and for 2 weeks have been teased with “one more detailed reading to get heart age-“ why on Earth is it not counting the more recent ones? Zero directions or way to ask questions regarding the app.
  10. [R24] Instant Heart Rate 3/5 · US lost readings with update: App was working great for me. Recently did the update and lost almost all my BP readings. Lost the entire month of July and most of August.
  11. [R34] Instant Heart Rate 2/5 · US Not at all what I thought: Mainly got this app for B/P. The app would only take my pulse
  12. [R1] Instant Heart Rate 1/5 · US Not Free: Not Free
  13. [R4] Instant Heart Rate 1/5 · US Not happy: Cancelled membership but was still charged 64 for something I never even used
  14. [R6] Instant Heart Rate 3/5 · US Nice app: Overall it’s a nice app, me personally I found better. I uninstalled the app after using it for a few hrs and realized it isn’t for me. But ever since it keeps trying to charge my card 64$ I went back to delete my whole account and it tried to charge my card again! Good thing is my card was locked.
  15. [R10] Instant Heart Rate 1/5 · US Bad privacy: I bet nobody actually reads the privacy policy. Read it.
  16. [R13] Instant Heart Rate 2/5 · US Pushy: Kind of pushy that another app needs you to make an account to use it(presumably to sell your info)
  17. [R28] Instant Heart Rate 1/5 · US They try to charge you fast: They tried to take 60 dollars before the free trial was even over! Dont use this.
  18. [R37] Instant Heart Rate 1/5 · US Finger BP?: Several of this type of health app advertise having the ability to take BP directly from a finger. Blatant false advertising and they all need to take that down. If you want BP you will have to have a BP cuff.
  19. [R65] Cardiio 5/5 · US No blood monitors: I’m enjoying the app but the only issue I have is that there is no blood monitor
  20. [R19] Instant Heart Rate 1/5 · US Terrible do NOT get.: my friend wanted me to get this app to reacted to different names when she mentioned them, and it DOESN’T work at all. It keeps telling me to gently place my index finger over my camera lens, but I do MULTIPLE times and it doesn’t work! I also have a pretty new IPhone so it should work.
  21. [R39] Instant Heart Rate 3/5 · GB Almost works sometimes: This is a very clever app making use of the rear camera and the light, and when it works it takes about 30s, and when it doesn't you can spend 30 minutes trying different fingers and placing it near the light over the light at different angles and the app just doesn't want to detect your finger.
  22. [R58] Instant Heart Rate 2/5 · US Junk: It rarely works for pulse reading. By the time it can finally detect a pulse, it’s an at rest beat, worthless.

Synthesized from 120 recent App Store reviews · updated July 2026 · View on the App Store