Retro 15C vs RLM
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Retro 15C
This app emulates a classic RPN scientific calculator, offering advanced features like complex number arithmetic, matrix calculations, and programmability. It provides a functional and complex tool reminiscent of 1980s calculators.
- Complex number arithmetic
- Matrix calculations
- Numerical root finder
- Numerical integration
- Statistical functions
- Programmable
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Students and scientists from the 1980s will remember the classic RPN scientific calculators. These calculators strike a perfect balance between functionality and complexity. * Complex number arithmetic and trig functions * Matrix calculations * Numerical root finder * Numerical integration * Statistical functions, linear regression * Fully programmable This app is completely free, no ads or extra bits to buy. I love this calculator and I like to share.
RLM
This app is a scientific and programmable calculator designed for science and engineering, replicating the functionality of the HP-11C. It offers extensive features for finance, business, statistics, complex numbers, and unit conversions, with a programmable interface for custom calculations.
- Finance calculations (amortization, bond price, Black-Scholes)
- Business functions (break-even, currency exchange)
- Statistical analysis (regression, probability distributions)
- Scientific functions (complex numbers, logarithms, trigonometry)
- Unit and currency conversions
- Programmable interface for custom scripts
- Equation solver
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The RLM-11C+ application is a general purpose calculator with a special focus science and engineering. It is based in the Hewlett-Packard HP-11C calculator, but specially designed to bring up the most of your iOS devices and , at the same time, conserving the easy of use and all functions 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: Calculations with Cash Flows occurring at regular time intervals. •Unequal Periods: Calculations with Cash Flows occurring at arbitrary dates. •Depreciation: Calculates depreciation with SL, SOYD, DB or MACRS methods and conventions. values at sight. •Interest Conversion: 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. •Logarithms, Trigonometric, Hyperbolic and Number Alteration functions. •Triangle Solution: Solves a Plane & Spherical triangles. •3D Vectors: Operations and functions with vectors in Cartesian, Spherical or Cylindrical coordinates. •Universal Constants: All the NIST-CODATA physical constants values and descriptions. •Units Conversion: Physical units conversion completely customizable. >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. •Storage Registers: Store and perform operations directly over the calculator’s storage registers. •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 rating: Retro 15C at 4.3 against RLM's 3.1. Retro 15C also leads on in-app purchases (none vs 4) and ratings volume (233 vs 7). RLM's advantage is update cadence (every 5 weeks vs every 53 months). On price, 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
Both are free to download. RLM sells 4 in-app purchases, starting at $0.49 per month. Retro 15C asks for nothing beyond the download.
Retro 15C holds the better App Store score, 4.3 against 3.1. That said, the two scores are not equally well evidenced: Retro 15C has 233 ratings behind it against 7, so its average is the more settled of the two. Written reviews point the same way: 76% of Retro 15C's written reviews are positive against 67% of RLM's.
Retro 15C ships an update every 53 months, RLM every 5 weeks. The most recent releases landed on October 26, 2026 and October 24, 2026 respectively.
| Parameter | Retro 15C | RLM |
|---|---|---|
| Price | Free | Free |
| Rating | 4.3 (233 ratings) — better | 3.1 (7 ratings) |
| Positive reviews | 76.1% of reviews — better | 66.7% of reviews |
| Number of ratings | 233 — better | 7 |
| Update frequency | Every 53 months | Every 5 weeks — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Free — better | Free with in-app purchases |
| Devices | iPhone, iPod | iPhone, iPad, iPod — better |
| Requires iOS | 8.0 — better | 15.0 |
| Further details — not scored | ||
| Size | 5 MB | 6 MB |
| Age rating | 4+ | 4+ |
| Developer | Greg Hewgill | R.L.M. Software |
Customer experience
Retro 15C
RLM
Bugs and requests
Retro 15C
Reported bugs
4 issues- Blinking display with large calculations
- Bugs with HMS conversions
- Inability to close app on newer iPhones
- Stopped working with iOS 14 updates
Requested features
5 requests- Add haptic feedback on key presses
- Implement continuous memory to save settings and programs
- Add portrait mode option
- Improve compatibility with newer iOS versions
- Add copy/paste functionality for stack and registers
RLM
Not enough reviews yet to summarise bugs or requests.
In-app purchases
Retro 15C
No in-app purchases
RLM
- Monthly Subscription$0.491 Month
- Semi-Annual Subscription$2.996 Months
- Annual Subscription$5.991 Year
- Lifetime Purchase$9.99







