Category documentation
Calculators: instructions and references
A useful calculator shows its assumptions instead of hiding a number behind a button. LittleKit’s maths tools update as you type, reject invalid input and explain the formula or algorithm used for the result.
Choosing a tool: Enter values in the units and convention named by the page, then compare the displayed formula with your question. For money, change the assumptions rather than treating an estimate as an offer; for statistics, decide whether the data represents a sample or a full population.
16 tool references, grouped by category. Searches stay in this tab.
Calculators
Browse category Calculators
Mortgage Repayment CalculatorMonthly payment = P × r ÷ (1 − (1 + r)^−n), where P is principal, r is nominal annual rate ÷ 12, and n is term in months.Percentage CalculatorResult = percentage ÷ 100 × number.Percentage ChangeChange = (new − original) ÷ |original| × 100.Percentage DifferenceDifference = |a − b| ÷ ((a + b) / 2) × 100.Ratio CalculatorDivides both integer terms by their greatest common divisor.Fraction CalculatorUses common denominators for addition/subtraction and cross products for multiplication/division, then reduces by GCD.Average CalculatorArithmetic mean = sum of values ÷ count.Median CalculatorSorts values; returns the middle value or mean of the two middle values.Standard Deviation CalculatorWelford’s algorithm accumulates squared deviations.GCD CalculatorEuclid’s remainder algorithm finds the greatest common divisor.LCM CalculatorLCM(a,b) = |a ÷ GCD(a,b) × b|, folded across the list.Prime Number CheckerTests divisibility by 2 and odd integers through the square root.Scientific CalculatorA bounded recursive-descent parser supports + − * / % ^, parentheses, pi, e, sin/cos/tan, inverse trig, sqrt, abs, ln, log, exp, floor and ceil.Random Number GeneratorWeb Crypto rejection sampling gives each integer in the inclusive range equal probability.Decimal ↔ FractionFinite decimals become an integer over a power of ten, then reduce by GCD.Roman Numeral ConverterUses standard subtractive Roman notation: IV, IX, XL, XC, CD and CM.