Comparison

Calc Engine vs Countdown Days

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

Head to head
About

Calc Engine

A highly customizable calculator with advanced features like graphing, equation solving, and unit conversion. Design your own keyboards and functions to streamline your workflow across Apple devices.

Highlights
  • Customizable keyboard layouts
  • User-defined functions and constants
  • Live equation graphing
  • Equation solving
  • Extensive unit conversions
  • Programmer mode (hex, binary, octal)
  • Cross-device syncing
Features
Read full description

Calc Engine™ — The Calculator That Fits How You Work Whether you're splitting a dinner bill, plotting an equation, or working through bitwise logic, Calc Engine meets you where you are. It's a beautiful, fully customizable calculator that grows with you — and syncs seamlessly across iPhone, iPad, Mac, and Apple Watch. Make it look and feel like yours • Choose from rich color themes to match your style • Pick the fonts and key shapes that feel right in your hands • A calculator you actually enjoy opening Design keyboards your way • Build your own keyboard pages — drag any key from a curated library onto a 4×5, 5×5, or 6×5 grid • Mix digits, operators, scientific functions, your own constants — anything you reach for often, all in one place • Set a long-press alternate on any key so a single tile handles a primary and secondary action • Name each keyboard, pick its icon, and reorder it alongside the standard pages — your custom keyboards show up right where you'd expect them • Enable or disable any page (built-in or custom) per device Build your personal math library • Define your own functions with up to three parameters — name them whatever makes sense to you • Save the constants you use all the time and insert them with a single tap • Full calculation history, automatically saved — scroll back anytime Powerful math, always within reach • Trig (radians or degrees), logarithms, exponentials, roots, and more — there when you need them, out of the way when you don't • Live results as you type, so you always know where you're headed • Per-function rounding built in — perfect for money, measurements, or anything that needs a clean output Convert between hundreds of units in seconds • Tap a value, then any two units to see the conversion live — miles to km, lb to kg, °F to °C, gal to L, anything you need • 250+ built-in units across 40+ categories: length, mass, volume, temperature, time, speed, angle, energy, power, pressure, electrical, magnetic, optical, radioactivity, data, and more • Favorite the categories you actually use so they sit at the top — synced across your devices automatically • Build your own functions with conversions baked in — define a formula once and reuse it forever See your equations come to life in graphs • Plot equations like x = y² or sin(x) live as you type, right beside the keyboard • Tap any graph to expand into a full-screen view for closer inspection • A dedicated graphing keyboard with x, y, and = keeps everything in one place — no separate app, no separate mode Solve equations as you type • Type x² = 121 or sin(x) = 0.5 and Calc Engine finds every real answer • Tap the solved answers to reuse it in your next calculation, no separate "solve" mode Programmer mode without leaving the calculator • Type hex (0x), binary (0b), and octal (0o) literals — read and write the way you read code • A full bitwise toolkit: AND, OR, XOR, NOT, shifts, and rotates • Every result shown in HEX, DEC, OCT, and BIN simultaneously, with configurable word size (8/16/32/64) and signed/unsigned interpretation • Tap the binary row to expand into a byte-by-byte view with bit-position labels Private by design • Everything syncs through your personal iCloud — nothing stored on our servers • Fully localized and native on every Apple platform Unlock Calc Engine+ for the full experience — custom themes, fonts, key shapes, custom keyboards, user-defined functions, saved constants, unit conversions, live graphing, equation solving, programmer-mode hex/binary/bitwise, and more. Everything that makes Calc Engine truly yours. Teach it your formulas once. Customize it to feel like home. Use it forever.

About

Countdown Days

Features
Read full description

Countdown Days: Events & Widgets Every day brings you closer to something worth celebrating. Countdown Days helps you make every moment count with reminders, widgets, and beautiful customization. From birthdays and anniversaries to vacations, exams, project deadlines, and life's biggest milestones, create beautiful events, organize them with sub-events, and track every countdown in one easy-to-manage place. Keep every important moment beautifully organized and always within reach. Powerful Countdown Features - Count down to any future date or count up from past events - View days remaining or days elapsed at a glance - Add an optional end date for events with a duration - Organize related events with sub-events for easier management - Repeat events every N days, weeks, months, or years - Receive reminders on the event day, 1 day before, or 1 week before - Add beautiful Home Screen widgets in multiple styles - Customize event icons, colors, and title highlights - Protect private categories with Face ID or Touch ID - Enjoy a clean, distraction-free experience with no ads Perfect For - Birthdays - Anniversaries - Weddings - Vacations - Holidays - Exams - Project deadlines - Retirement - Baby due dates - Sporting events - Concerts - Flights - Personal goals - Every moment worth celebrating Designed for People Around the World Countdown Days supports multiple calendar systems, making it easy to track important dates wherever you live. Supported calendars include: - Gregorian - Chinese Lunar - Islamic - Indian - Buddhist - Japanese - Hebrew Smart Time Zone Support Choose how countdowns handle time zones. Keep events fixed to their original time zone, or automatically adapt them to your current location, making Countdown Days perfect for everything from international flights to local celebrations. Unlock Even More with Pro Some advanced features require Countdown Days Pro, including cloud sync, additional customization options, and more. Download Countdown Days today and start looking forward to every special moment. Icon Credits: https://countdowndays.pages.dev/icon-credits Useful Links Privacy policy: https://countdowndays.pages.dev/privacy Terms of use: https://countdowndays.pages.dev/terms Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Calc Engine4 screens
Countdown Days4 screens

Verdict

The call

The clearest difference is update cadence: Calc Engine at daily against Countdown Days's every 5 weeks. Countdown Days's advantage is iOS requirement (15.6 vs 18). On price, 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

Both are free to download. Calc Engine sells 1 one-off in-app purchase and Countdown Days sells 3 in-app purchases, starting at $1.29 per month. Whichever you choose, the download price is not the number that matters.

UpkeepUpdate frequency

Calc Engine ships an update daily, Countdown Days every 5 weeks. The most recent releases landed on October 16, 2026 and October 9, 2026 respectively.

Scorecard2 real differences · 7 level
Calc Engine versus Countdown Days: the parameters behind the verdict, then further details
ParameterCalc EngineCountdown Days
PriceFreeFree
Rating5.0 (4 ratings) — better—
Number of ratings4 — better—
Update frequencyDaily — betterEvery 5 weeks
AdsNoNo
In-app purchasesYesYes
MonetizationFree—
DevicesiPhone, iPad, Mac, Apple Watch — betteriPhone, iPad, iPod
Requires iOS1815.6 — better
Further details — not scored
Size17 MB45 MB
Age rating4+4+
DeveloperVersaEdge Software, LLC长宏 侯

In-app purchases

1 purchases

Calc Engine

One-time1
  • Calc Engine+$9.99
3 purchases

Countdown Days

Subscriptions2
  • Pro (Monthly)$1.291 Month
  • Pro (Yearly)3 Days trial$9.991 Year
One-time1
  • Pro (Lifetime)$24.99

Questions

Is Calc Engine free?
Calc Engine is free to download, with in-app purchases available.
Is Countdown Days free?
Countdown Days is free to download, with in-app purchases available.
Do Calc Engine or Countdown Days have ads?
Neither Calc Engine nor Countdown Days shows ads.
Which is updated more often, Calc Engine or Countdown Days?
Calc Engine ships an update daily, and Countdown Days every 5 weeks. Most recently, Calc Engine was updated on October 16, 2026 and Countdown Days on October 9, 2026.

Other comparisons