Janus Calculator vs WP 31s
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Janus Calculator
This app offers a unique dual-calculator interface, supporting both standard and Reverse Polish Notation. It features programmable functions, extensive scientific and financial tools, and includes physical constants and an advanced option calculator.
- Dual calculator interface (Standard and RPN)
- Programmable functions
- Finance and scientific functions
- Physical constants
- Black-Scholes option calculator
- Implied value calculation
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Two-sided calculator. Side A uses Standard Notation, Side B uses Reverse Polish Notation. Both calculators are programmable, include various finance and scientific functions, and the values of 45 physical constants. Also includes a Black-Scholes option calculator, including calculation of implied values for each of the inputs.
WP 31s
This app emulates a classic RPN scientific calculator, offering a rich function set for daily use with a simplified interface. It's based on the more complex WP 34s but is designed for easier operation.
- RPN scientific calculator emulation
- Rich function set
- Simplified, less cluttered keyboard
- Based on WP 34s
- Available on iOS
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WP 31s is a classic RPN scientific calculator based on the powerful but more complex WP 34s. Now available on iOS too (see the support site for other emulators and for the real stuff). It is not programmable but has a rich function set for daily use and is easier to use, thanks to a less cluttered keyboard. A manual can be downloaded at http://sourceforge.net/projects/wp34s/files/doc/Manual_wp_31s_1_2q.pdf/download
Screenshots
Verdict
The clearest difference is rating: WP 31s at 4.9 against Janus Calculator's 2.0. WP 31s also leads on update cadence (every 10 months vs every 45 months) and review sentiment (100% vs 83%). On price, ads, in-app purchases and monetization model 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.
WP 31s holds the better App Store score, 4.9 against 2.0. That said, the two scores are not equally well evidenced: WP 31s has 15 ratings behind it against 1, so its average is the more settled of the two. Written reviews point the same way: 83% of Janus Calculator's written reviews are positive against 100% of WP 31s's.
Janus Calculator ships an update every 45 months, WP 31s every 10 months. The most recent releases landed on October 4, 2026 and October 11, 2026 respectively.
| Parameter | Janus Calculator | WP 31s |
|---|---|---|
| Price | Free | Free |
| Rating | 2.0 (1 ratings) | 4.9 (15 ratings) — better |
| Positive reviews | 83.3% of reviews | 100.0% of reviews — better |
| Number of ratings | 1 | 15 — better |
| Update frequency | Every 45 months | Every 10 months — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 26.2 | 12.0 — better |
| Further details — not scored | ||
| Size | 1 MB | 16 MB |
| Age rating | 4+ | 4+ |
| Developer | Geoffrey Domm | Pascal Meheut |
Customer experience
Janus Calculator
WP 31s
In-app purchases
Janus Calculator
No in-app purchases
WP 31s
No in-app purchases
