Enter — RPN Calculator
Scientific and financial RPN
Free · In‑App Purchases
Free, with a true four-level stack and undo. Enter Pro adds the scientific functions and a financial keyboard with the HP-12C's function set: loans, cash flows, bonds.
Enter is a Reverse Polish Notation calculator with a true four-level stack — for people who think in RPN and are tired of hunting for the equals key. Free to download, with every everyday function included.
There are no parentheses and there is no equals. Type a number, press ENTER, type another, press the operation. The answer is already there.
A TRUE FOUR-LEVEL STACK
X, Y, Z and T, with T replicating as the stack drops — so a constant stays where you put it and repeated operations simply work. LAST x brings back the argument the previous function consumed. Roll up, roll down, exchange X and Y. Ten numbered storage registers that survive a relaunch.
THE FUNCTIONS
• Arithmetic, powers, roots and reciprocals
• Sine, cosine and tangent with their inverses, in degrees, radians or gradians
• Hyperbolics and their inverses
• Natural and common logarithms with their exponentials
• Percent and percent change, integer and fractional parts, absolute value, modulo, factorial
• Combinations and permutations, polar and rectangular coordinates, decimal hours to hours-minutes-seconds
• Twelve significant digits, shown as FIX, SCI, ENG or ALL
A FINANCIAL KEYBOARD
Switch keyboards for a financial calculator with the HP-12C's function set. The five keys — n, i, PV, PMT and FV — store or solve, the way HP's financial calculators have always worked: key in what you know and press the one you want. Amortization schedules rounded to the cents on the statement. Cash flows with NPV and IRR. Bond price and yield to maturity. Straight-line, sum-of-the-years'-digits and declining-balance depreciation. Simple interest on 360- and 365-day bases, percent of total, dates and days between dates, and the statistics keys with linear regression. Hold n, i, PV, PMT or FV to see what it is holding.
UNDO, AND A PAPER TAPE
Fifty levels of undo and redo, covering the stack, the registers, and whatever you were part-way through typing. The paper tape prints every number and every function beside its result — tap any line to lift that value straight back onto the stack. It survives a relaunch and copies out as text.
CONVERSIONS AND CONSTANTS
Ten quantities — length, mass, temperature, volume, area, speed, pressure, energy, power and force — with exact factors wherever the definition is exact. Twenty physical and mathematical constants, searchable, carried at full precision rather than rounded to the display.
ON THE MAC
The whole keyboard: digits, operators, Return for ENTER, Escape to clear, letters for the functions. A menu bar carrying the stack operations and the display modes with their shortcuts.
FREE, WITH ENTER PRO
Free: the stack, arithmetic, square roots and squares, reciprocals, percentages, the ten storage registers, undo, and the rest of the everyday keys.
Enter Pro, one purchase with no subscription, unlocks the scientific functions — trigonometry, logarithms, exponentials and powers — and the financial keyboard, along with the paper tape, conversions, constants and the extended function list. It covers every iPhone and Mac on your Apple Account, and Family Sharing.
Bought Enter before it was free? Everything stays unlocked.
DESIGNED, NOT PORTED
Keys that depress under your finger, and a keyboard of its own when you turn the iPhone on its side. Properly typeset notation — real superscripts, and a radical drawn to the weight of the type around it. A two-line display showing Y above X, so you always know what the stack is holding.
PRIVATE
No accounts. No analytics. No tracking. Nothing you calculate leaves your device.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
A financial keyboard, with the HP-12C's function set.
• n, i, PV, PMT and FV that store or solve, as on HP's financial calculators
• Amortization, simple interest, and BEGIN/END payment timing
• Cash flows with NPV and IRR; bond price and yield
• Straight-line, sum-of-the-years'-digits and declining-balance depreciation
• Dates and days between dates, in M.DY or D.MY
• Σ+, means, standard deviations and linear regression
• STO with + − × ÷ to combine a register with X
• Hold a financial key to see what it is holding
The financial keyboard is part of Enter Pro. Switch between the two keyboards with the orange legend above the gear, or in Settings.
The developer, Bastiaan Meelberg, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Bastiaan Meelberg
- Size
- 984.1 KB
- Category
- Utilities
- Compatibility
Requires iOS 18.0 or later.
- iPhone
Requires iOS 18.0 or later. - Mac
Requires macOS 15.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Enter Pro $7.99
- Copyright
- © 2026 FM Software Development
