Other Calculators

Aspect Ratio Calculator Find the aspect ratio of any width and height, such as 1920 × 1080 = 16:9, or resize to a new width or height while keeping the same ratio.
Bandwidth Calculator The connection speed needed to move data in a set time, or the monthly data and average bandwidth a website uses.
Birthday Paradox Calculator The chance that two people in a group share a birthday, how many people give any target probability, and the chance someone shares yours.
Character Counter Count characters with and without spaces, letters, digits and punctuation, bytes and SMS messages, and check text against post and SEO limits.
Coin Flip Simulator Flip a virtual coin once or up to 10,000 times, with the heads and tails count, the longest streak and how likely the result was.
Color Converter Convert colours between HEX, RGB, HSL, HSV and CMYK, with the colour's luminance and whether white or black text reads best on it.
Contrast Ratio Calculator Check the contrast ratio between text and background colours and whether it passes WCAG AA and AAA for normal text, large text and interface parts.
Cribbage Hand Calculator Score a cribbage hand or crib from four cards and the starter: fifteens, pairs, runs, flushes and his nobs, with a full breakdown.
Dice Roller Roll virtual dice — any number of d4, d6, d8, d10, d12, d20 or d100 with a modifier — and see the total, the average and the odds of your roll.
Doubling Time Calculator How long a quantity takes to double at a steady growth rate, exactly and by the rule of 72, or the halving time for a decline.
Download Time Calculator How long a download or upload takes from the file size and your connection speed, with overhead, the real transfer rate and the speed needed for a target time.
DPI Calculator The DPI (dots per inch) of a print from the image's pixels and the printed size, with print quality and the largest size at 300 DPI.
File Size Calculator Convert file and storage sizes between bytes, KB, MB, GB and TB, their binary KiB, MiB, GiB and TiB equivalents, and bits.
Image Resize Calculator New pixel dimensions for an image resized by a percentage, to a width or height, or to fit inside a box, keeping the aspect ratio.
Lottery Odds Calculator Odds of winning any lottery from the numbers picked and the pool size, with bonus balls, odds of matching fewer numbers and the effect of more tickets.
Map Scale Calculator Convert map distances to real distances and back at any scale such as 1:25,000, or find a map's scale from a known distance.
Number to Words Converter Write any number out in English words — whole numbers, decimals and negatives, ordinals like twenty-first, and cheque style — in US or British style.
Password Generator Generate strong random passwords of any length with letters, digits and symbols, optionally without look-alike characters, with their strength in bits.
Password Strength Calculator Check how strong a password is: its entropy in bits, how long a brute-force attack would take, and whether it uses common patterns attackers try first.
Print Size Calculator How large an image can be printed at a chosen DPI, in inches and centimetres, and the DPI it reaches at common print sizes from 4 × 6 to 20 × 30.
Raffle Odds Calculator Your chance of winning a raffle from your tickets, the total sold and the number of prizes, with expected prizes and the tickets needed for a 50% chance.
Random Number Generator Generate random whole numbers between any minimum and maximum — one or many, with or without repeats, sorted if you like — with an optional seed.
Readability Score Calculator Score how easy any English text is to read with Flesch Reading Ease, Flesch–Kincaid grade, Gunning fog, Coleman–Liau and ARI.
Scale Model Calculator Convert real sizes to model sizes, or model sizes back to real ones, at any scale such as 1:24, 1:72 or HO 1:87.
Screen Size Calculator Width and height of a TV, monitor or phone screen from its diagonal and aspect ratio, in inches and centimetres, with pixel density (PPI).
Sim Racing FOV Calculator Calculate the correct field of view for sim racing from your screen size, aspect ratio and eye distance, for single or triple screens.
Syllable Counter Count the syllables in any word, sentence or poem, word by word and line by line, with the average syllables per word.
Text Case Converter Convert text to UPPER CASE, lower case, Title Case, Sentence case, camelCase, PascalCase, snake_case, kebab-case or CONSTANT_CASE.
Tire Size Calculator The diameter, sidewall height, circumference and revolutions per km of a tire from its size, and how a new size compares.
Video Bitrate Calculator The file size of a video from its bitrate and length, or the video bitrate needed to hit a target file size.
Wind Chill Calculator The wind chill temperature from air temperature and wind speed, in metric or imperial units, with the frostbite risk.
Word Counter Count words, characters, sentences and paragraphs in any text, with reading and speaking time and the most used words.

A Guide to Other Calculators

This category is honest about what it is: the calculators that do not belong to one of the fourteen subject areas. That does not make them marginal. Several are among the most used on the site, because the questions they answer come up constantly and have nowhere obvious to live.

Thirty-two calculators, grouped below by what they actually do rather than by subject.

Images, screens and print

Seven calculators for working with pixels and physical sizes. The Aspect Ratio Calculator finds the missing dimension that preserves proportions, which is the single most common image-handling calculation there is. The Image Resize Calculator does the same job framed around resizing to a target.

The DPI Calculator and Print Size Calculator connect pixels to physical dimensions, which is where most printing disappointment comes from. An image is only as large as its pixel count allows at an acceptable density: a 1,200 by 1,800 pixel photo is a good six by four inch print at 300 dpi and a poor twelve by eight.

The Screen Size Calculator derives width, height and pixel density from a diagonal and an aspect ratio, since a screen is sold by its diagonal alone and that does not determine its shape.

Two cover colour. The Color Converter moves between hex, RGB, HSL and related formats, and the Contrast Ratio Calculator computes the ratio between two colours and checks it against the accessibility thresholds. That second one is worth running on anything you publish: a contrast ratio below 4.5 to 1 for body text fails the standard, and designers miss it constantly because the text looks fine to someone with unimpaired vision on a good screen.

Files, bandwidth and transfer

Four calculators for digital quantities. The File Size Calculator and Video Bitrate Calculator relate duration, quality and size, which is the arithmetic behind every decision about export settings.

The Download Time Calculator and Bandwidth Calculator handle the conversion that causes the most confusion in consumer technology: connection speeds are quoted in bits per second and file sizes in bytes, a factor of eight. A 100 Mbps connection moves about 12.5 megabytes each second, so a 5 GB file takes roughly seven minutes at full speed rather than the forty seconds the headline number suggests.

Text

Six calculators for working with words. The Word Counter and Character Counter cover the limits that applications, essays and social platforms impose, counting with and without spaces because different platforms count differently.

The Readability Score Calculator applies the standard readability formulas and reports the reading grade level, which is genuinely useful for anything written for a general audience. The Syllable Counter supports that and poetry alike, and it is honest that English syllable counting is rule-based and imperfect rather than exact.

The Text Case Converter switches between sentence, title, camel and snake cases, and the Number to Words Converter spells figures out, which cheques, legal documents and contracts all require.

Probability and chance

Three calculators where the answer is usually not what people expect. The Birthday Paradox Calculator gives the probability that two people in a group share a birthday, and the result is the best illustration in mathematics of how badly intuition handles combinations: in a group of 23 the chance is already above half, because there are 253 pairs rather than 23 people.

The Lottery Odds Calculator and Raffle Odds Calculator compute the real probability of winning, which is the most honest thing anyone can offer on the subject. They state the expected value as well, and these pages are not gambling advice: they exist so the odds are visible, which advertising for these products never makes them.

Random generators

Three tools rather than calculators. The Random Number Generator, Dice Roller and Coin Flip Simulator produce a fresh result each time, which is why they are the only pages on this site without a pre-computed example: a cached random number is not random.

The coin flip simulator also reports the longest run of the same side, which is instructive. In a hundred flips a run of five or six is entirely ordinary, and people asked to fake a random sequence almost never include one, which is how statisticians spot fabricated data.

Passwords and security

The Password Strength Calculator estimates how long a password would resist a brute-force attempt, and makes the point that length beats complexity: adding characters multiplies the search space far faster than adding symbol types does.

The Password Generator produces a random password in the browser, and nothing it generates is transmitted anywhere, because every calculation on this site runs locally. That is a design decision rather than a promise, and it is the only arrangement under which a web page should ever generate a password at all.

Scale and models

The Scale Model Calculator converts between real and model dimensions at any scale ratio, and the Map Scale Calculator does the same for map distances. The Doubling Time Calculator gives the time for a quantity to double at a growth rate, which applies to anything compounding.

Measurement odds and ends

The Tire Size Calculator decodes tyre markings and compares overall diameters, which matters because fitting a different size changes your speedometer reading and your gearing. The Wind Chill Calculator gives the apparent temperature from temperature and wind speed.

Games

The Cribbage Hand Calculator scores a hand under the full rules, which involve counting every combination that sums to fifteen and are famously easy to under-score. The Sim Racing FOV Calculator computes the geometrically correct field of view from screen size and viewing distance, so that the virtual view matches what your eyes would see at that distance.

The two conversions worth memorising

Two factors in this category explain most of the confusion people have about digital quantities, and both are worth knowing without a calculator.

Eight bits make a byte. Network speeds, streaming bitrates and connection advertising are all quoted in bits; files, storage and downloads are in bytes. Dividing a megabit figure by eight gives the megabytes per second, and that single division resolves nearly every question about why a download is slower than the connection promised.

Storage is counted two ways. Manufacturers use powers of ten, so a terabyte is a trillion bytes. Operating systems traditionally use powers of two, where a terabyte is about ten percent larger. That is the whole explanation for a 1 TB drive showing as roughly 931 GB: nothing is missing and nobody is cheating, the two are counting in different bases.

Together those two factors account for the gap between what a device claims and what it appears to deliver, and neither is a defect.

Why these are grouped together

There is no subject linking a tyre size to a readability score. What links them is that each answers a question that is asked often, has a definite answer, and does not sit inside health, finance, maths or any of the other categories.

The alternative would be to force them into a category they do not fit, which helps nobody looking for them, or to leave them out, which would remove some of the most used pages here. Grouping them by function, as above, is the arrangement that makes them findable.

If you arrived here looking for something specific and it is not listed, the search covers every calculator on the site by name and by what it does, which is usually faster than working out which of fifteen categories something was filed under.