RPN vs Refuel Buddy
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN
This app is a photo-realistic simulation of the classic HP-25 scientific calculator. It offers advanced programming features, a vast function library, and modern enhancements for enhanced usability on iOS devices.
- Photo-realistic simulation
- Programmable (99/999 steps)
- 15 user-defined function keys
- 100 symbolic labels
- 100 visible registers
- Program library with 150+ programs
- Over 270 functions
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RPN-25 CE is a photo-realistic simulation of Hewlett-Packard's highly popular scientific calculator HP-25 for the iPhone. Produced from August 1975 through 1978, it was the "Squash" member of the second-generation HP calculators known as the "Woodstock" series. It was also the first programmable calculator costing less than $200. RPN-25 CE simulates the HP-25C version released in July 1976. Its major improvement in that update was "Continuous Memory". While the simulator works just like the original calculator, a number of carefully designed extensions make it massively more powerful. Features: • Photo-realistic look • Programmable (99 or 999 steps), subroutines, conditional loops, branching • Insert and delete steps with automatic address correction • 15 user-defined function keys of up to 6 characters each, redefinable under program control • Programmable text messages • Program Auto-Start option upon loading • 100 symbolic labels • 100 visible registers, "non-volatile", with unrestricted store/recall arithmetic • 100 flags, visible at a glance • Single-step constants • Program comments • Program library with more than 150 programs pre-installed • More than 270 functions and operations not available on the HP-25 • 100 sounds built-in • Much faster than the original • "Live" register view supporting user interaction (run/stop, single-stepping) • "Live" stack view • Thousands separator (optional) • High-contrast display (optional) • Selectable pause length (up to a day) • Program listing view with program title and description • Program library view • Store, name and retrieve any number of programs • Sharing: Files, iCloud Drive, e-mail, AirDrop, Dropbox, copy, paste, print • Import and run RPN-32 CE and GO-25 programs • Run a large number of HP-41 programs with little or no changes • Clock display (AM/PM or 24h) • Supports Dark Mode Calculator functions: • Statistics, including clearing statistics registers only • Factorial for arbitrary arguments • Trigonometric functions (degrees, radians, grads) • Polar/rectangular conversions • Inverse, square root, logarithm, exponential, Pi • Percentage • Storage arithmetic (store and recall) • Extended stack operations • Low-battery warning • Sound alerts • ..and many, many more Details: cuveesoft.ch/rpn25
Refuel Buddy
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Refuelling Calculator / Refuel Buddy app is to help tech crew in calculating the fuel distribution & discrepancy of fuel uplift on narrow body aircraft with ( LEFT , RIGHT, CENTER ) three tanks configuration. The app included two different display formats to choose from and Smart features will calculate & adjust automatically on center tank figures on full wing tanks condition.
Screenshots
Verdict
The clearest difference is update cadence: RPN at every 2 months against Refuel Buddy's every 22 months. RPN also leads on iOS requirement (12.0 vs 15.1). Refuel Buddy's advantage is price ($1.99 vs $2.99). On ads, in-app purchases and device support 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
RPN costs $2.99 and Refuel Buddy $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.
RPN ships an update every 2 months, Refuel Buddy every 22 months. The most recent releases landed on November 3, 2026 and October 25, 2026 respectively.
| Parameter | RPN | Refuel Buddy |
|---|---|---|
| Price | $2.99 | $1.99 — better |
| Rating | 4.3 (10 ratings) — better | — |
| Positive reviews | 80.0% of reviews | — |
| Number of ratings | 10 — better | — |
| Update frequency | Every 2 months — better | Every 22 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Paid | — |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 12.0 — better | 15.1 |
| Further details — not scored | ||
| Size | 28 MB | 6 MB |
| Age rating | 4+ | 17+ |
| Developer | CuVee Software | htin kyaw |
In-app purchases
RPN
No in-app purchases
Refuel Buddy
No in-app purchases









