ThetaCalc vs HP
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
ThetaCalc
This utility app provides a Reverse Polish Notation (RPN) calculator. Users can extend its functionality by programming custom functions and equations using JavaScript.
- Reverse Polish Notation (RPN) calculator
- User-programmable functions
- JavaScript equation support
- Extensible functionality
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ThetaCalc is a RPN (Reverse Polish Notation) calculator which can be extended by functions and equations programmed by the user in JavaScript.
HP
Emulates classic Hewlett Packard RPN scientific calculators from the 1970s. Experience the original HP-35, HP-45, and HP-21 models on your iPhone.
- RPN calculator emulation
- HP-35 model
- HP-45 model
- HP-21 model
- Classic scientific calculator interface
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The classic Hewlett Packard RPN (Reverse Polish Notation) calculators. - HP-35, HP-45. First pocket scientific calculators (1972). - HP-21. 2nd gen of the HP-35 (1975)
Screenshots
Verdict
The clearest difference is rating: HP at 5.0 against ThetaCalc's 4.3. HP also leads on update cadence (every 11 days vs every 3 months). On price, review sentiment, ratings volume and ads there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
HP holds the better App Store score, 5.0 against 4.3. Both are backed by a comparable volume of ratings — 4 and 5 respectively. Written reviews split almost evenly too, at 100% and 100% positive.
ThetaCalc ships an update every 3 months, HP every 11 days. The most recent releases landed on June 1, 2026 and September 21, 2026 respectively.
| Parameter | ThetaCalc | HP |
|---|---|---|
| Price | Free | Free |
| Rating | 4.3 (4 ratings) | 5.0 (5 ratings) — better |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| Number of ratings | 4 | 5 — better |
| Update frequency | Every 3 months | Every 11 days — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad — better | iPhone |
| Requires iOS | 17.6 | 17.2 — better |
| Further details — not scored | ||
| Size | 1 MB | 2 MB |
| Age rating | 4+ | 4+ |
| Developer | Felix Stehli | Enrique Haro |
Customer experience
ThetaCalc
HP
In-app purchases
ThetaCalc
No in-app purchases
HP
No in-app purchases
