Designed, programmed, and used by two internal medicine docs, Acid Plus is an essential tool for healthcare professionals who need quick, detailed, and easy-to-interpret acid-base results from ABGs and metabolic panels.

Ideal for MDs, PAs, RNs, RTs, EMTs, and med students, everything you need for acid-base calculations is put right in the palm of your hand. No more clunky ABG websites or guesswork.

With an intuitive design and easy-to-read display, Acid Plus makes it a breeze to answer even the most complex acid-base problems in seconds. Just turn the device to landscape view to get a colorful graph with an arrow highlighting the disorder.

*** What Others Say **************

• "This is certainly the best ABG calculator that we have seen so far on the iPhone and iPod Touch."
- Firas Salim,

• "If you are practicing medicine and own an iPhone, you need to have it."
- Igor Kovic, MD,

• "Interpreting the ABG and electrolytes to understand the acid-base status in my patients just turned from a chore into something immensely enjoyable. I cannot help smiling whenever I start this application."

• "This program is awesome! You have no idea how much this helps. Thank you so much."


• Fast, accurate input using the dial
• Primary calculations including partial and complete compensations using anion gap with delta delta
• International support for kPa
• Ability to discern complex acid/base problems with secondary disorders
• See the anion gap and delta delta displayed on-screen with metabolic acidoses
• Detailed views listing common causes of the primary acid-base disorder
• On-the-fly derivation of anion gap, delta-delta, and base excess
• Rotating your device right or left to landscape view reveals a colorful interactive acid-base graph
• Interactive graph helps visualize acid-base disorders quickly and powerfully
• Set your own institution's anion gap easily for personalized results
• Save and recall your most recent ABG for quick review
• Works on iPhone and iPad

If you like the program please rate it. If you have any concerns or find any bugs please contact us at

DISCLAIMER: Please consider that the results provided by this program are intended to supplement but not substitute for the expertise and clinical judgment of a healthcare professional. The results and accompanying educational material are provided as is, and Free Radical does not warrant that they are accurate or up to date, although that is certainly our goal.

What’s New

Version 3.0.4

- Fixed a bug with the wrong column of the dial responding when entering ABG data

New in Version 3:
- Completely redesigned look and feel
- Interactive graph
- Detailed results at your fingertips
- On-the-fly derivation of anion gap, delta-delta, and base excess
- Even more accurate calculator
- Easy sharing of interesting ABGs
- Steps allows you to view how a result was derived

Ratings and Reviews

5.0 out of 5
11 Ratings

11 Ratings

broken.jar ,

So great to see this app return!

I’ve been missing this for a while but all the extra details available and being able to set the graph manually are really useful. Great update, thanks!

Merqtio77 ,

So useful

Not only is it easy to use but there’s just so much detailed info available. Really helpful to be able to see how all the results are derived.

Lakki ,

Love this ABG app

The perfect app for the wards. The picker for choosing values is great.

App Privacy

The developer, Free Radical Software, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Linked to You

The following data may be collected but it is not linked to your identity:

  • Purchases

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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