How to Use OmniCalc

Getting started

OmniCalc opens on a home screen made of cards, one per tool. Pick a card to open that tool. On first launch you see a working calculator and a short tour that you can dismiss.

Moving around

• Use the arrows (or ← / →) in the carousel to browse the cards. A grid view is available in Settings.
• Ctrl+K searches tools, Alt+H returns home, Alt+1 to 8 open the first eight home cards, Ctrl+, opens Settings.
• In the calculators, digits and operators type straight in when no field is focused. Enter or = evaluates, Esc clears.

Keyboard shortcuts apply mainly to the Windows version. Everything is also reachable with taps or clicks.

Installation

Android (APK)

1. Download the APK on your phone from the Downloads page. Requires Android 7.0 (API 24) or newer.
2. Open the file. Because it is not installed from an app store, Android asks you to allow installs from your browser or file manager. The exact setting name differs between phones.
3. Tap Install, then open OmniCalc.

Windows 64-bit installer

1. Download the installer and run it. Windows 10 or 11 (64-bit).
2. The installer is not code-signed, so Windows SmartScreen may warn you. Choose More info, then Run anyway.
3. Pick an install folder if you want, finish the wizard, and start OmniCalc from the Start menu or desktop shortcut.

Windows portable

1. Download the portable file and put it in any folder.
2. Double-click to run. No installation step. The same SmartScreen notice may appear.

Standard Calculator

What it does

Everyday arithmetic with a live preview of the answer while you type, memory keys, percentages, expression editing and one-click copy.

Where to find it

On the home screen, open the Standard Calculator card (or press Ctrl+K and search for it).

How to use it

• Type or tap an expression such as 12 + 8 × 3. The preview updates as you go.
• Press = to finish. The next operation continues from the full-precision value, so 1 ÷ 3 × 3 gives exactly 1.
• Press Ctrl+C (with no text selected) to copy the result. ↑/↓ in the expression box recall earlier expressions.

Example

200 + 10% gives 220, because A + B% means A + A×B/100.

Common mistakes

• Expecting 200 + 10% to be 210.
• Typing malformed thousands separators like 1,23. They are rejected, never guessed.

Scientific Calculator

What it does

Trigonometry (plus inverse and hyperbolic), logarithms, powers and roots, factorials, nCr and nPr, with a DEG/RAD switch and compact or expanded layouts.

Where to find it

On the home screen, open the Scientific Calculator card (or press Ctrl+K and search for it).

How to use it

• Choose DEG or RAD first, then enter the expression.
• For a logarithm with another base type log(x, base) in the field. Constants available: pi, e, tau, phi, i.
• The EXP key adds a power of ten to the current number: 2 ÷ 5 EXP 3 is 2/5E3 = 0.0004.

Example

In DEG mode, sin(30) gives 0.5.

Common mistakes

• Forgetting the angle mode.
• Entering 5 cm. Unit symbols are not supported here; use the Unit Converter.
• Expecting √(−4) to work. It is a domain error unless the “Allow complex results” option is on.
• Reading very large integers: beyond 2⁵³ numbers are shown in scientific notation because doubles are no longer exact.

Percentage

What it does

Eight common percentage questions in one tool.

Where to find it

On the home screen, open the Percentage card (or press Ctrl+K and search for it).

How to use it

• Pick a mode: What is X% of Y?, X is what percentage of Y?, Percentage increase, Percentage decrease, Percentage change (old → new), Reverse (X is P% of what?), Discount, or Markup on cost.
• Fill in the two labelled boxes with plain numbers (no % sign) and read the result rows.

Example

Discount mode with original price 80 and 25% gives 60.

Common mistakes

• Swapping the two boxes: read each label (part vs whole, old vs new).
• Typing the % symbol into a number box.

Date & Time

What it does

Date differences, adding or subtracting time, exact age, leap-year facts and time-zone conversion.

Where to find it

On the home screen, open the Date & Time card (or press Ctrl+K and search for it).

How to use it

• Choose a date tool: Difference, Add / subtract, Age, Leap year or Time zones.
• Enter the dates (for Age: Date of birth and Age on). “Today” means your local calendar date.
• For zone-aware tools enter an IANA zone name such as Asia/Karachi or Europe/London.

Example

Difference between two dates returns the span between them; Leap year shows the days in February and in the year.

Common mistakes

• Typing zone abbreviations like PST instead of IANA names.
• Expecting hours to behave like days: years, months, weeks and days keep the same clock time across daylight-saving changes, while hours and minutes are exact elapsed time.

Graphing

What it does

Plots one or more functions (Cartesian and polar), with pan, zoom, estimated intersections and a table of values.

Where to find it

On the home screen, open the Graphing card (or press Ctrl+K and search for it).

How to use it

• Type a function in the Function box, for example x^2 - 4 or sin(x), and add more if you want to compare them.
• Adjust the View range, then pan and zoom the plot.
• Use Intersections (estimates) to compare a First and a Second function. Use Table of values with Start x, Step and Rows.

Example

Plot x^2 - 4: the curve crosses the x-axis at −2 and 2.

Common mistakes

• Treating intersections as exact: they are estimates.
• Blank plot: the plotting library loads when the tool opens. The table of values shows the same data meanwhile.

Equation Solver

What it does

Solves one equation with one unknown or a linear system. Roots are checked by substituting them back.

Where to find it

On the home screen, open the Equation Solver card (or press Ctrl+K and search for it).

How to use it

• Mode One equation: type the equation, optionally name the Variable (it is auto-detected). Linear, quadratic and polynomial equations up to degree 10 are supported; other equations use a numeric scan between the search range minimum and maximum.
• Mode Linear system: one equation per line. The tool reports a unique solution, no solution, or infinitely many.
• Repeated roots are listed once with their multiplicity. Step-by-step working exists for linear and quadratic equations only.

Example

x^2 - 5x + 6 = 0 gives x = 2 and x = 3. The system 2x + y = 5 / x - y = 1 gives x = 2, y = 1.

Common mistakes

• Expecting general symbolic algebra. OmniCalc does not do that.
• Using a search range that does not contain the root of a non-polynomial equation.

Matrices

What it does

Add, subtract, multiply, scalar multiply, transpose, determinant, inverse, rank and trace, up to 20×20.

Where to find it

On the home screen, open the Matrices card (or press Ctrl+K and search for it).

How to use it

• Enter Matrix A (and Matrix B when the operation needs it).
• Choose the Operation, set Scalar k if needed, and read the result.

Example

The determinant of [[1, 2], [3, 4]] is −2.

Common mistakes

• Multiplying matrices whose sizes do not match.
• Asking for the inverse or determinant of a non-square matrix, or the inverse of a singular one.

Vectors

What it does

Add, subtract, scale, dot and cross products, magnitude, angle between vectors and unit vectors.

Where to find it

On the home screen, open the Vectors card (or press Ctrl+K and search for it).

How to use it

• Enter Vector A and Vector B with components separated by commas or spaces.
• Choose the Operation. The cross product is 3D only.

Example

A = (1, 2, 3) and B = (4, 5, 6): the dot product is 32.

Common mistakes

• Using vectors of different lengths.
• Asking for a cross product of 2D vectors.

Complex Numbers

What it does

Sum, difference, product, quotient, power, conjugate, magnitude, argument (degrees or radians), polar to rectangular conversion and all n-th roots.

Where to find it

On the home screen, open the Complex Numbers card (or press Ctrl+K and search for it).

How to use it

• Enter z₁ (and z₂ if needed) using i for the imaginary unit, for example 3+4i.
• Pick the operation and read the rectangular and polar results.

Example

(1+2i)(3+4i) = −5 + 10i.

Common mistakes

• Writing j instead of i.
• Mixing up the argument in degrees and in radians.

Statistics

What it does

Count, sum, mean, median, mode, minimum, maximum, range, sample and population variance and standard deviation, quartiles, interquartile range and a frequency table. CSV import and export are supported.

Where to find it

On the home screen, open the Statistics card (or press Ctrl+K and search for it).

How to use it

• Enter your numbers (or import a CSV).
• Read the summary. Quartiles use the median-of-halves method.

Example

Data 2, 4, 4, 4, 5, 5, 7, 9: mean 5, population standard deviation 2, sample standard deviation about 2.14.

Common mistakes

• Using the sample figure when you have the whole population, or the reverse.
• Comparing quartiles with software that uses a different quartile method.

Number Theory

What it does

Prime test, prime factorization, divisors, GCD, LCM, divisibility, quotient and remainder, using exact integer arithmetic up to 200 digits.

Where to find it

On the home screen, open the Number Theory card (or press Ctrl+K and search for it).

How to use it

• Enter an integer to analyse it, or a list of integers for GCD and LCM.
• Numbers up to 10¹⁵ are factored immediately. Larger ones need the “Factor in background” button. It runs for up to 10 seconds, can be cancelled, and incomplete answers are labelled PARTIAL.

Example

GCD of 48 and 18 is 6 and their LCM is 144.

Common mistakes

• Treating a PARTIAL factorization as complete.
• Forgetting that primality is exact below about 3.3×10²⁴ and “probable” above it.

Number Bases

What it does

Converts between binary, octal, decimal, hexadecimal and any base from 2 to 36, with two’s-complement and bit-pattern views.

Where to find it

On the home screen, open the Number Bases card (or press Ctrl+K and search for it).

How to use it

• Enter the Value and choose the Input base.
• Read the conversions. Use Custom base (2–36) for other bases and Two’s complement width for signed values.

Example

Decimal 255 is binary 11111111 and hexadecimal FF.

Common mistakes

• Using digits that do not exist in the input base (for example 2 in binary).

Unit Converter

What it does

Converts within 15 categories, including length, mass, temperature, speed, area, volume, time, data storage, energy, power, pressure, angle and frequency.

Where to find it

On the home screen, open the Unit Converter card (or press Ctrl+K and search for it).

How to use it

• Choose a category, then the From and To units, and type a value.
• Temperature uses offsets correctly (not just ratios). Data storage distinguishes decimal and binary units. Regional units such as marla and kanal show both common definitions, clearly labelled.

Example

100 °C is 212 °F.

Common mistakes

• Trying to convert between different kinds of quantity (for example length to mass).
• Entering compound units such as km/h to m/s as free text. Use the Speed category instead.

Custom Conversions

What it does

Your own ratios (for example a currency pair) that you can create, edit, rename, duplicate, favorite, search, delete, export and import. Optional live exchange rates are available.

Where to find it

On the home screen, open the Custom Conversions card (or press Ctrl+K and search for it).

How to use it

• Create a conversion by entering the ratio you want.
• Optional: press Download rates to fetch exchange rates. This is the only time OmniCalc contacts the internet. The source, time retrieved and a warning when the rates are over 24 hours old are shown.

Example

If you enter 1 USD = 280 PKR as your own ratio, converting 10 USD gives 2,800 PKR. The 280 is only your example, not a rate OmniCalc claims is current.

Common mistakes

• Treating a ratio you entered as a live market rate.
• Expecting live rates without an internet connection. Your own ratios still work offline.

Formula Library

What it does

More than 50 STEM formulas you can calculate with, plus your own custom formulas.

Where to find it

On the home screen, open the Formula Library card (or press Ctrl+K and search for it).

How to use it

• Search or browse by category, open a formula and fill in the known values.
• Add custom formulas, mark favorites, and import or export your formulas.

Example

Pick a geometry formula, enter the sides you know and read the result.

Common mistakes

• Assuming units are enforced: they are shown for information only, so use consistent units yourself.
• Expecting every formula to be rearrangeable. Rearrangements are written individually for each formula.

Calculation History

What it does

A saved list of past calculations that you can search, filter, reuse, favorite, delete, clear and export as CSV, TXT or JSON.

Where to find it

On the home screen, open the History card (or press Ctrl+K and search for it).

How to use it

• Open History, search or filter, and choose an entry.
• Reuse works for the Standard and Scientific calculators. Long histories load 100 entries at a time.

Example

Search “sin” to list your trigonometry calculations.

Common mistakes

• Expecting history to sync between devices. It is saved on the device you use.

Favorites

What it does

One place for the tools, calculations, formulas and conversions you starred.

Where to find it

On the home screen, open the Favorites card (or press Ctrl+K and search for it).

How to use it

• Star an item where you see the star. Open Favorites to return to it quickly.

Example

Star a conversion you use every week.

Common mistakes

• Looking for favorites on another device. They are stored locally.

Settings & Themes

What it does

Appearance, calculation and data options.

Where to find it

On the home screen, open the Settings card (or press Ctrl+K and search for it).

How to use it

• Theme: light, dark or follow the system. Also accent colour, text size, high contrast, reduced motion and optional click sounds.
• Calculation: precision (12 significant digits by default), number notation and DEG/RAD default. Home screen: carousel or grid.
• Backup: export or import everything as JSON. Import can Merge with or Replace existing data. Resetting preferences and deleting saved data are separate actions.

Example

Switch to dark theme, raise the text size, then export a backup.

Common mistakes

• Importing with Replace without exporting a backup first.

Troubleshooting

• Windows SmartScreen warning: expected for an unsigned installer. Choose More info, then Run anyway, but only for files from the official release page.
• Android refuses to install: allow installs from the app you used to download the file, then open the APK again. Your phone must run Android 7.0 or newer.
• “Your latest changes could not be saved”: the storage may be full or read-only. The app keeps retrying. Settings → export backup always works.
• Saved data looks reset: the app keeps a backup copy when stored data is damaged and shows a recovery banner.
• A blank graph: use the table of values under the graph, then reopen the tool.
• Answers differ in the last digits: calculations use standard floating-point numbers. Adjust the precision in Settings.

Still stuck? Use the Contact page to report a bug.