All Math Tools
Fraction Calculator
Add, subtract, multiply or divide fractions, simplified automatically.
OpenRatio Calculator
Simplify a ratio, or scale it to find a missing value.
OpenAverage Calculator
Mean, median, mode and range from any list of numbers.
OpenStandard Deviation Calculator
Population and sample standard deviation, with variance and mean.
OpenTip Calculator
Tip amount and per-person split for any bill.
OpenGPA Calculator
Weighted GPA from your course grades and credit hours.
OpenBill Splitter
Split a restaurant bill fairly when everyone didn't order the same amount.
OpenRandom Number Generator
Pick random numbers in a range, with or without repeats.
OpenRandom Team & Name Picker
Paste a list of names, split into random teams or pick random winners.
OpenTrip Expense Splitter
Track group expenses on a trip and see exactly who owes whom, simplified.
OpenBinary, Hex & Decimal Converter
Convert numbers between binary, octal, decimal and hexadecimal.
OpenRoman Numeral Converter
Convert between numbers and Roman numerals, both directions.
OpenZodiac Sign Calculator
Find your zodiac sign from a birth date, with dates and traits.
OpenWhat Day Was I Born
Find the exact day of the week you were born, plus fun facts.
OpenCountdown Timer
Count down to any date and time — a birthday, launch or deadline.
OpenReaction Time Test
Test how fast you react to a visual cue, in milliseconds.
OpenMental Math Speed Drill
A timed arithmetic drill — pick the operations and race the clock.
OpenPrime Number Checker & Factoriser
Test primality, get the full factorisation, divisors and nearest primes.
OpenLCM & HCF Calculator
LCM and HCF of any set of numbers, with the working shown.
OpenQuadratic Equation Solver
Roots, discriminant, vertex and factored form for any quadratic.
OpenNumber to Words Converter
Spell any number out in words, including cheque and invoice wording.
OpenVisual Memory Test
Squares flash on a grid — tap the ones you saw, and the grid keeps growing.
OpenNumber Memory Test
A sequence of digits appears, then vanishes. Type it back, one digit longer each level.
OpenAim Trainer
Hit thirty targets as fast as you can, with accuracy measured alongside speed.
OpenChimp Test
Click the numbers in order from memory — the task chimpanzees beat humans at.
OpenAbout these tools
Twenty-five calculators for the arithmetic that comes up constantly but is easy to get wrong by hand. The everyday ones — percentages, fractions, ratios, averages and rounding. The school and coursework ones — quadratic equations, simultaneous equations, factorials, prime factors, LCM and HCF, logarithms and trigonometry. And the statistics side — standard deviation, variance, permutations and combinations.
Each one shows its working rather than just the answer, which is the difference between getting a number and being able to check it — or hand it in.
Nothing here needs an account, and nothing you put into any of them is uploaded or stored. Every tool is a single page that does one job, so you can bookmark the one you use and skip this page entirely next time.
Checking the answer, not replacing the working
These tools are most useful as a second opinion. Working a problem through by hand and then confirming the result catches arithmetic slips without hiding the method, which is the opposite of what happens when a calculator is used to skip the working entirely. For anyone studying, that distinction is the whole point — an exam will ask for the method, and a tool that produces the answer teaches nothing about how to get there.
Where they genuinely save time is in the repetitive middle of a problem. Factorising a large number, finding a common denominator across several fractions, or computing a standard deviation across thirty values is mechanical work where mistakes are easy and instructive value is low.
What the statistics tools will and will not tell you
The average calculator gives the mean, median and mode, and choosing between them is more consequential than calculating any of them. The mean is pulled hard by extreme values; the median is not. Nine salaries of 40,000 and one of 500,000 give a mean of 86,000, which describes nobody in the group, and a median of 40,000, which describes a typical case accurately.
Standard deviation adds the missing dimension: how spread out the values are. Two datasets can share an identical mean while one is tightly clustered and the other scattered, and the mean alone cannot distinguish them. A useful quick check on any dataset is to compute both the mean and the median — if they are close, the data is roughly symmetrical, and if they differ substantially, something is pulling the mean and the median is the safer figure to report.
Everything runs on your device
No data you enter is uploaded, and none of these tools require an account or impose a limit on how many times you use them. That includes the memory and speed tests in this section, whose scores are kept in your browser's local storage on the device you are using rather than on any server.