RPN vs RLM
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN
This app emulates the first pocket scientific calculator, offering a photo-realistic vintage experience. It simulates original operating speeds and unique arithmetic bugs, with optional modern enhancements like non-volatile registers.
- Photo-realistic look-and-feel
- Multiple vintage skins
- Vintage and Enhanced modes
- Optional key-click and key-glow
- Swipe to correct input
- Display stack and memory registers
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On January 4, 1972, Hewlett-Packard announced the HP-35, world's first scientific calculator small enough to fit in a pocket - more precisely, Bill Hewlett's shirt-pocket. The HP-35 was an immediate hit with students, engineers, and scientists. Despite its steep price of $395 (about $3000 today), it sold ten times better than anticipated in the first year. Experience this unique calculator that won HP the prestigious "IEEE Milestone in Electrical Engineering and Computing" in 2009. Features: • Photo-realistic look-and-feel • Three skins: version 1, versions 2 & 3 (1973) and final version 4 (1974) • Vintage mode and Enhanced mode • Key-click and key-glow, both optional • Swipe left across display to correct number input errors • Cut/copy/paste display value • Display stack registers and memory registers • All decimal points but one light when iPhone battery charge drops below 5% Vintage mode In this mode, peculiarities of a real HP-35 are simulated: - original speed of operation - stack register Z copied to T on trig functions - leading zeros may be entered; zero can be made negative - a negative number may be entered by pressing CHS before or after the number - a keyboard entry or RCL immediately following STO does not raise the stack - for version 1 only: simulation of a number of known arithmetic bugs Enhanced mode - non-volatile stack and registers - use registers 1 through 9 with HP-45-like register arithmetic - register 0 works as LastX register
RLM
This advanced scientific calculator emulates the functionality of the HP-15C, offering comprehensive tools for finance, business, statistics, and scientific calculations. It supports programming, equation solving, and unit conversions, optimized for iOS devices.
- Programmable advanced scientific calculator
- Finance and business calculation menus
- Statistics and probability functions
- Complex numbers and matrix operations
- Unit and currency conversions
- Equation solver and programming capabilities
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The RLM-15CX application is a programable advanced scientific calculator. It is based in the Hewlett-Packard HP-15C calculator, but specially designed to bring up the most of your iOS devices and , at the same time, conserving the easy of use and the functionality originally provided by the real calculator. >Finance Menu: •Account Balance: Credit line type account based on cash transactions and interest rates applied. •Amortization: Loan Amortization Schedule for a single loan payment or from several payments at once. •Bond Price & Yield: Bonds calculations in an easy way with all options and values at sight. •Black-Scholes Options: CALL, PUT and “Greeks” calculations of the Black-Scholes European option valuation model. •Equal Periods Cash Flows: Solve problems where different cash flows occur at regular time intervals. •Unequal Periods Cash Flows: Solve problems where different cash flows occur at different dates. •Depreciation: Calculates depreciation with SL, SOYD, DB or MACRS methods and conventions. values at sight. •Interest Rates: Nominal and effective interest conversion. •Time Value of Money: Compound Interest problems involving money earning interest over a period of time. >Business Menu: •Bill-Tip-Split: Calculates the sharing of a Bill with Tip. •Break-Even: Analyze the following relation: Profit = (Price - Var.Cost) • Units - Fix.Cost •Currency Exchange with on-line rates. •Percents & Margins: Calculates %Change, %Total and Business margins. >Date / Time Menu: Calculates Date and Time intervals with all values at sight. >Statistics Menu: •One-Variable Statistics: Calculations for one variable data samples. •Two-Variable Statistics: Calculations for two variables data samples. •Curve Fitting: 6 Regression models to fit a curve based on two variables data samples. •Probability: Combinations, permutations, Normal, Exponential, t-Student and Weibull probability distributions. >Scientific Menu: •Complex Numbers: Operations and functions with complex numbers. •Matrix: view, create or edit matrices with real or complex elements. •Plane Triangle: Solves a two dimensional triangle (ASA,SAS,SSA and SSS). •Spherical Triangle: Solves a triangle in a sphere’s surface (AAA,AAS,ASA,SAS,SSA and SSS). •Universal Constants: All the NIST-CODATA fundamental physical constants. •Vectors 3D: Operations and functions with vectors in Cartesian, Spherical or Cylindrical coordinates. >Convert Menu: •Angles & Polar: Convert angles between DEG,RAD,GRAD,DMS or Slope % & Polar-Rectangular coordinates. •Currencies: world currencies conversions with manual input or on-line current rates. •Interest Rates: Nominal and effective interest conversion. •Units: Physical units conversions. >Program Menu: Create, edit or load previously saved programs. >Solver Menu: Solve arbitrary algebraic equations entered and saved in the equation editor and creates a menu with all the variables to solve any of them. >Utilities Menu: •General Settings: Customize the calculator to your preference. •Memory Content: Shows all memory content edit, backup or restore. •Help Documents: learn by example about all menus. >Editors: submenu to select data editors. System requirements: iOS 15.0 or above. 30 days Free-Trial. In-App-Purchase: One-Payment for life. License Agreement: http://www.apple.com/legal/itunes/appstore/dev/stdeula Disclaimer: THIS IS NOT A HEWLETT PACKARD CALCULATOR, AND IS NOT SPONSORED IN ANYWAY BY HEWLETT PACKARD OR ANY OF ITS SUBSIDIARIES
Screenshots
Verdict
The clearest difference is price: RLM at Free against RPN's $1.99. RLM also leads on update cadence (monthly vs every 6 months) and review sentiment (80% vs 71%). RPN's advantage is in-app purchases (none vs 4) and rating (4.4 vs 4.1). On ratings volume, ads 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
RLM is free to download; RPN costs $1.99 up front. RLM sells 4 in-app purchases, starting at $0.49 per month. RPN asks for nothing beyond the download.
RPN holds the better App Store score, 4.4 against 4.1. Both are backed by a comparable volume of ratings — 14 and 18 respectively. Written reviews complicate that: 71% of RPN's written reviews are positive against 80% of RLM's, so the app with the better star average is not the one people write more warmly about.
RPN ships an update every 6 months, RLM monthly. The most recent releases landed on November 1, 2026 and October 30, 2026 respectively.
| Parameter | RPN | RLM |
|---|---|---|
| Price | $1.99 | Free — better |
| Rating | 4.4 (14 ratings) — better | 4.1 (18 ratings) |
| Positive reviews | 71.4% of reviews | 80.0% of reviews — better |
| Number of ratings | 14 | 18 — better |
| Update frequency | Every 6 months | Monthly — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Paid | Free with in-app purchases — better |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 12.0 — better | 15.0 |
| Further details — not scored | ||
| Size | 14 MB | 6 MB |
| Age rating | 4+ | 4+ |
| Developer | CuVee Software | R.L.M. Software |
Customer experience
RPN
RLM
In-app purchases
RPN
No in-app purchases
RLM
- Monthly Subscription$0.491 Month
- Semi-Annual Subscription$2.996 Months
- Annual Subscription$5.991 Year
- One-Time Purchase$9.99








