Calculator · Windows 10 and 11

A calculator that shows the answer as you type

Type 120 × 1.2 or 200 + 10% and the answer is already there. Switch on Scientific for powers, roots and sines, click an old result in the history to use it again. Beside it, every converter and calculator people search for, and a coin, dice, random numbers and a wheel of names for when chance should decide.

Updated 9 October 2026

Octoolo's Calculator showing 4.99 × 12 = 59.88 above the keypad, with earlier sums such as 200 + 10% = 220 in the history.

What you can do in the Calculator

Scientific calculatorType whole calculations with powers, roots, logs and trig, and watch the answer. Unit converterLength, weight, temperature, area, volume and speed, in every unit at once. Percentage calculatorX% of Y, what percent one number is of another, and the percent change. Days between datesDays, weeks, months and weekdays between two dates, with or without the last day. Age calculatorExact age in years, months and days, days lived, and days to the next birthday. Aspect ratio calculatorReduce any width and height to a ratio like 16:9 and size it to a new width. Discount calculatorSale price, what you save and the total with sales tax, from any percent off. Data size converterBytes to petabytes, in decimal or binary units, and why 1 TB shows as 931 GB. Roman numeralsNumbers to Roman numerals and back, 1 to 3999, with the subtractive rules. BMI calculatorBody mass index from height and weight, in cm and kg or feet and pounds. Time zone converterOne time shown in every city you add, with daylight saving worked out for the date. Loan calculatorMonthly payment, total paid and total interest for any amount, rate and term. Tip calculatorTip, total and each person's share of a bill, for any tip percent and group size. Days from todayThe date any number of days, weeks, months or years before or after a day. Time calculatorHours between two times, sums of hours and minutes, and a weekly timesheet. Fraction calculatorAdd, subtract, multiply and divide fractions and mixed numbers, with the working shown. GPA calculatorYour term and cumulative GPA from courses, credits and letter grades, weighted or not. Grade calculatorYour weighted grade so far, and the score you need on the final for the grade you want. Compound interest calculatorHow savings grow with interest and monthly deposits, year by year, with a chart. Calorie calculatorCalories a day to keep, lose or gain weight, from the Mifflin-St Jeor equation. Flip a coinHeads or tails with a tossed coin, a tally of every flip, and up to 10,000 flips at once. Dice rollerRoll up to 100 dice of 4 to 100 sides, add a modifier, and keep a history of rolls. Random number generatorRandom whole numbers or decimals between any two values, with or without repeats. Wheel of namesSpin a colored wheel to pick a name or a winner, remove winners, and save your lists.

The calculator

Type a whole calculation, with brackets, and the answer shows as you type. 200 + 10% is 220, 2π is 6.28…, and missing brackets are closed for you. The Scientific switch adds powers, roots, π, e, factorials, sine, cosine and tangent in degrees or radians, and logarithms. The last fifty calculations stay in the history.

Converters and everyday sums

Units: length, weight, temperature, area, volume and speed. Data sizes from bytes to petabytes.
Percentages, discounts and tips and bill splitting.
Days between dates, age and time zones.
Loans, BMI, aspect ratios and Roman numerals.
Days from a date (working days too) and a time calculator with a weekly timesheet.
Fractions with the working shown, a GPA and a grade calculator.
Compound interest with a chart and a year-by-year table, and a calorie calculator.

And when chance should decide

Flip a coin (up to 10,000 at once, with a tally), roll dice from d4 to d100 with a modifier, draw random numbers with or without repeats, or spin a wheel of names with saved lists. Every result comes from the computer's cryptographic random source, drawn so each outcome is exactly as likely.

Questions, answered

Does it replace the Windows Calculator?

It does the everyday sums differently: you type the whole calculation and see the answer live. It has no programmer or graphing mode.

Does it work offline?

Yes, all of it.

Can I use the keyboard?

Yes. Type the calculation, press Enter or = for the result and Escape to clear.

Does it keep my history?

Yes, the last fifty calculations, on your computer. You can clear them.

Can it flip a coin or pick a random number?

Yes. Flip a coin, Roll dice, Random number generator and Wheel of names are in the Chance group, all drawing from the computer's cryptographic random source.

The Calculator, and 16 more apps.

Download for Windows

7 days free, then from $3.99 a month for all 17 apps. Windows 10 and 11.

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