Math & Statistics Tools
Percentages, averages, deviation, significance and ratio maths, each with the working shown rather than just an answer.
Built for students, analysts, researchers. 19 tools published.
Attendance Calculator
Every absence raises the number of future sessions needed to recover, because the denominator grows alongside the numerator.
📊Compound Growth
Percentages multiply, they do not add. Apply a sequence of changes and see where you actually end up, including what it takes to recover a loss.
📊Decimal to Fraction
Putting the digits over a power of ten is exact and useless. Continued fractions find the simplest fraction that is close enough — the same method that gives 355/113 for π.
📊Final Grade Calculator
What do I need on the final to pass? Says plainly when a target is out of reach, and shows the whole range of outcomes rather than one number.
📊Fraction Calc
Fractions are exact and decimals are not. This keeps integers all the way through and only rounds when it prints.
📊Grade Recovery Path
Translate earned points and remaining weight into a required future average.
📊Mean Median Mode
All three centres at once, with the working shown and a distribution plot that makes it obvious when they disagree — which is exactly when the average is misleading you.
📊Missing Data Range
Compute best and worst feasible means from declared value bounds rather than one imputed guess.
📊Percent of Total
Three equal parts are 33.3% each, which sums to 99.9. Rounding each value correctly does not fix it. Largest-remainder allocation does.
📊Percentage Calc
Three different questions share the word percentage, and a fall is never undone by a rise of the same size.
📊Percentage Change
Four related questions in one place — change between two numbers, apply a percentage, find the original, and see the working written out so you can check it.
📊Percentage Error
Same two numbers, same gap of 50. The answer depends entirely on which one you divide by — which is why the choice has to be justified.
📊Pooled Standard Deviation
Weight sample variances by their degrees of freedom instead of averaging standard deviations.
📊Probability to Odds
Translate a percentage probability into odds for and odds against.
📊Progress ETA
A progress bar extrapolates from the last instant. Measuring over a longer window is the whole reason a manual estimate is better.
📊Randomization Plan
Allocate participant IDs across arms inside blocks while preserving exact counts and audit order.
📊Reverse Percentage
The sale price is £80 after 20% off — what was it before? Not £96. Adding a percentage back is not the same as taking it off, and this shows why.
📊Wide to Long CSV
Turn wide repeated-measure columns into tidy variable and value rows.
📊Z-Score Percentile
Show left-tail percentile, upper tail and two-sided tail from one standard-normal z-score.