Everyday

Work out percentages, what-percent, and percent change in one place.

Calculate the tip and split the total bill between people.

Work out how many floor or wall tiles you need for a room — from its length and width and the tile size, with an adjustable waste allowance and boxes required.

Calculate Body Mass Index from height and weight, with a healthy range.

Calculate exact age in years, months, days — and find your next birthday.

Project how a starting balance grows with regular contributions, your interest rate, and your compounding frequency.

Calculate the monthly payment, total interest, and full amortization schedule for any fixed-rate loan.

Distraction-free scratch pad that autosaves to your browser — no account, no upload, no ads.

A click counter that survives a refresh — multi-counter, custom step, goal alert, and keyboard shortcuts.

Estimate your basal metabolic rate, daily calorie needs, and cut/maintain/bulk targets — Mifflin-St Jeor formula.

Calculate the dew point and absolute humidity from temperature and relative humidity using the Magnus formula, with a comfort rating in °C or °F.

Calculate the wind chill — how cold the air feels — from temperature and wind speed, in metric or imperial, in your browser.

Find the best bedtime or wake time aligned to 90-minute sleep cycles so you wake up between cycles, not mid-deep-sleep.

Calculate the sale price after a percent or fixed discount — plus tax, savings, and effective discount rate.

Estimate your due date from LMP, conception date, or ultrasound — see current weeks and trimester.

Estimate body fat percentage from height, neck, waist (and hip for women) using the US Navy tape-measure formula.

Compute your 5 training zones from age and resting HR — pick max-HR formula (Tanaka / Fox / Gulati) and method (%MHR or %HRR / Karvonen).

Split your daily calories into grams of protein, carbs, and fat — IIFYM-style presets for balanced, low-carb, high-protein, or keto.

Validate an International Bank Account Number — checks country code, length, and the mod-97 checksum. Supports 75+ countries.

Validate a card number with the Luhn checksum, detect brand (Visa/MC/Amex/etc), and check expected length. Local, no network.

Pour-over, French press, AeroPress, espresso, cold brew — calculate coffee and water amounts from any ratio with method-specific defaults.

Scale bread recipes by baker's percentage — enter your flour weight and each ingredient as a percentage of flour to get exact gram weights, total dough weight and hydration.

Compute your weighted GPA across courses on US 4.0, US 4.3 (+ grades), or Korean 4.5 scales. Tracks total credits and quality points.

Estimate daily water needs from weight, activity, climate, and pregnancy/breastfeeding status — gives a target and a 4-block schedule.

Validate ISBN-10 and ISBN-13 checksums and convert between the two formats. Hyphens and spaces are handled.

Calculate or verify the GS1 modulo-10 check digit for EAN-13, UPC-A and EAN-8 barcodes. Enter the data digits to get the check digit, or a full code to confirm it is valid.

Factor an integer into primes, list all divisors, and compute GCD and LCM of two numbers. Handles values up to ~10¹².

Generate the Collatz sequence for any positive integer — halve when even, triple-plus-one when odd — and see the number of steps, the peak value reached and the full path to 1.

Generate the first N Fibonacci numbers — 0, 1, 1, 2, 3, 5, 8 … — with exact big-integer precision, and see the last term, the running sum and the golden-ratio approximation of the final two terms.

Compute nCr and nPr, with and without repetition, plus factorials — exact arbitrary-precision integers for probability, lottery odds and combinatorics.

Compute a^b mod m exactly for arbitrarily large integers using fast binary exponentiation, plus the modular multiplicative inverse of the base. Ideal for RSA, Diffie-Hellman and number-theory work.

Estimate what any appliance costs to run — enter its wattage, hours per day and your rate per kWh to get daily, weekly, monthly and yearly energy and cost.

Solve a right triangle from any two sides — get the third side, both acute angles, area and perimeter using the Pythagorean theorem.

From two points, get the slope, the line equation y = mx + b, the distance, midpoint, angle of inclination, and rise/run.

Solve a proportion a/b = c/d — enter any three values, leave one field empty, and the fourth is found by cross-multiplication.

Enter any one of radius, diameter, circumference or area, and instantly get the other three — with the formulas shown.

Estimate the fuel cost of a trip from the distance, your vehicle's fuel economy and the fuel price — in metric (L/100km) or US (mpg), with an optional round trip.

Estimate ideal body weight from height and sex using the Devine, Robinson, Miller and Hamwi formulas — plus the healthy weight range for a normal BMI.

Check that your microphone works, watch the input level and waveform live, and record a clip. The audio never leaves your device.

Work out the score you need on your final exam to hit the course grade you want — plus your best and worst possible outcomes.

Solve ax² + bx + c = 0 with the quadratic formula — real or complex roots, plus discriminant, vertex, axis of symmetry and sum/product of roots.

Estimate password strength via entropy and crack-time. Detects common passwords, sequences, and repeated characters. Nothing leaves your browser.

Show day of year, ISO 8601 week, quarter, Julian day, Unix timestamp, leap-year status, and year progress for any date.

Compute running pace, finish time, or distance from any two of them. Presets for 5K, 10K, half, and marathon.

Sum daily start/end times into a weekly total, subtract breaks, and split regular vs overtime. Optional hourly rate computes the paycheck.

Add tax to a net price or extract tax from a tax-inclusive price. Common VAT/GST/sales tax presets (5–25%).

Format a number the way each locale expects — `1,234,567.89`, `1.234.567,89`, `$1.23M`, `12 345 ₽` — and grab the matching JavaScript snippet.

Evaluate arithmetic expressions with the usual math functions — `sqrt`, `sin`, `log`, `pow`, `min/max`, and constants `pi`, `e`, `tau`.

Convert between hourly, weekly, monthly, and yearly pay — with configurable work week and paid holidays.

Compute Body Surface Area in m² using five published formulas — Mosteller, Du Bois, Haycock, Boyd, Gehan & George — side by side.

Convert between cups, tablespoons, teaspoons, millilitres, and fluid ounces — and weigh common ingredients in grams or ounces.

Pick a coffee / tea / cola dose and see how much caffeine is still in your bloodstream now, in an hour, in six — and when it'll drop below the sleep threshold.

Convert your dog or cat's age into the rough "human-year equivalent" — using vet-recommended scales, not the old multiply-by-seven myth.

Compare grocery and shopping items by price-per-unit (price per gram, mL, or piece). Mass, volume, and count groups with imperial and metric units.

Add, subtract, multiply, and divide fractions, mixed numbers, and decimals. Get the reduced fraction, mixed number, decimal, and worked steps.

Estimate your 1RM from a sub-maximal lift using six classic formulas (Epley, Brzycki, Lombardi, O'Conner, Wathan, Lander) plus a percentage projection table for programming training weights.

Compute the compound annual growth rate that connects a starting value to an ending value over N years — or solve for the end value or the time needed instead.

Solve for selling price, profit margin, or maximum cost — and convert between margin %, markup %, and price multiplier instantly.

Paste any list of numbers and instantly get count, mean, median, mode, standard deviation, quartiles, IQR, and more — all computed in your browser.

Paste (x, y) pairs and instantly get the best-fit line — slope, intercept, Pearson r, R², and a live prediction — all computed in your browser.