Comparison

RPN vs Refuel Buddy

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

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.

Highlights
  • 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
Features
Read full description

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

About

Refuel Buddy

Features
Read full description

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

RPN4 screens
Refuel Buddy3 screens

Verdict

The call

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

CostPrice · In-app purchases · Ads · Monetization

RPN costs $2.99 and Refuel Buddy $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

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.

Scorecard3 real differences · 7 level
RPN versus Refuel Buddy: the parameters behind the verdict, then further details
ParameterRPNRefuel Buddy
Price$2.99$1.99 — better
Rating4.3 (10 ratings) — better—
Positive reviews80.0% of reviews—
Number of ratings10 — better—
Update frequencyEvery 2 months — betterEvery 22 months
AdsNoNo
In-app purchasesNoNo
MonetizationPaid—
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS12.0 — better15.1
Further details — not scored
Size28 MB6 MB
Age rating4+17+
DeveloperCuVee Softwarehtin kyaw

In-app purchases

None

RPN

No in-app purchases

None

Refuel Buddy

No in-app purchases

Questions

Is RPN free?
RPN costs $2.99, with no in-app purchases.
Is Refuel Buddy free?
Refuel Buddy costs $1.99, with no in-app purchases.
Do RPN or Refuel Buddy have ads?
Neither RPN nor Refuel Buddy shows ads.
Which is updated more often, RPN or Refuel Buddy?
RPN ships an update every 2 months, and Refuel Buddy every 22 months. Most recently, RPN was updated on November 3, 2026 and Refuel Buddy on October 25, 2026.

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