Permutations & Combinations (nPr / nCr) Calculator

Percent of, percent change, and percent add/subtract in one.

Enter 2–6 positive integers to get the greatest common divisor (HCF / GCD) and least common multiple (LCM), with the Euclidean step chain shown.

Enter a list of numbers to get the mean, median, mode, range plus standard deviation, variance and total.

Enter the coefficients of ax² + bx + c = 0 to find the real or complex roots, discriminant and vertex.

Estimate a password's bit entropy, brute-force time and strength tier. All computation happens in your browser.

Convert between standard decimal numbers and scientific notation, with significant figures and order of magnitude.

Paste a list of numbers to compute mean, median, sample and population variance and standard deviation — with the working shown.

Solve a triangle from 3 sides, 2 sides + 1 angle, or 2 angles + 1 side — area, perimeter and remaining parts via the law of sines / cosines.

Given any two sides of a right triangle (two legs, or one leg plus the hypotenuse), instantly find the third side, area, perimeter and the two non-right angles.

Enter any one of radius, diameter, circumference or area to get the other three — useful for design, engineering and DIY.

Two-way conversion between Arabic numbers (1–3999) and Roman numerals (I, V, X, L, C, D, M) — handy for typesetting, chapter titles and homework.

Enter two points (x₁, y₁) and (x₂, y₂) to instantly get the slope, y-intercept, line equation y = mx + b, distance, and midpoint — a classroom staple for algebra and coordinate geometry.

Enter group size n to see the probability that at least two people share a birthday — the classic birthday problem.

Compute logₐ(x) for any base — natural log (ln), common log (log₁₀), binary log (log₂) and a custom base, with the change-of-base steps shown.

Enter a value, the mean and the standard deviation to compute the z-score and the corresponding normal-distribution percentile and probabilities.

Enter the screen resolution and diagonal size to get pixel density (PPI), real width/height, dot pitch and total pixel count.

Enter the number of tickets / selections and see the actual probability of hitting first, second … prizes in a Mark Six (6-of-49) draw.

Convert any decimal (including repeating decimals) to a simplified fraction and a mixed number.

Give a sphere any one of radius, diameter, surface area or volume and instantly get the other three — plus the great-circle circumference and area.

Enter the radius and height of a cylinder to get volume (π r²h), lateral surface, base area and total surface area.

Factor any integer from 2 up to 10¹² into primes, see the canonical exponent form, count and list all divisors.

Compute the n-th root of the product of n positive numbers — the right average for growth rates, returns and ratios — alongside the arithmetic mean for comparison.

Enter any integer n from 0 to 1500 to instantly compute F(n) and F(n−1) with BigInt precision, the consecutive-term ratio (converging to the golden ratio φ) and the first 30 terms of the sequence.