Mortgage Repayment Calculator
Monthly payment = P × r ÷ (1 − (1 + r)^−n), where P is principal, r is nominal annual rate ÷ 12, and n is term in months.
Calculators16 free tools
Calculators
Everyday numbers, with the working shown.
Most tool inputs are processed on your device.
16 of 16 tools
Percentage Calculator
Result = percentage ÷ 100 × number.
CalculatorsPercentage Change
Change = (new − original) ÷ |original| × 100.
CalculatorsPercentage Difference
Difference = |a − b| ÷ ((a + b) / 2) × 100.
CalculatorsRatio Calculator
Divides both integer terms by their greatest common divisor.
CalculatorsFraction Calculator
Uses common denominators for addition/subtraction and cross products for multiplication/division, then reduces by GCD.
CalculatorsAverage Calculator
Arithmetic mean = sum of values ÷ count.
CalculatorsMedian Calculator
Sorts values; returns the middle value or mean of the two middle values.
CalculatorsStandard Deviation Calculator
Welford’s algorithm accumulates squared deviations.
CalculatorsGCD Calculator
Euclid’s remainder algorithm finds the greatest common divisor.
CalculatorsLCM Calculator
LCM(a,b) = |a ÷ GCD(a,b) × b|, folded across the list.
CalculatorsPrime Number Checker
Tests divisibility by 2 and odd integers through the square root.
CalculatorsScientific Calculator
A bounded recursive-descent parser supports + − * / % ^, parentheses, pi, e, sin/cos/tan, inverse trig, sqrt, abs, ln, log, exp, floor and ceil.
CalculatorsRandom Number Generator
Web Crypto rejection sampling gives each integer in the inclusive range equal probability.
CalculatorsDecimal ↔ Fraction
Finite decimals become an integer over a power of ten, then reduce by GCD.
CalculatorsRoman Numeral Converter
Uses standard subtractive Roman notation: IV, IX, XL, XC, CD and CM.
CalculatorsA useful starting point
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.
Good reasons to use this category
- Checking a percentage, ratio or fraction
- Exploring a repayment or extra-payment scenario
- Summarising a small list of values
- Verifying a scientific expression with bounded functions
Choosing the right operation
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.
Know the boundary
Results are deterministic estimates, not financial, medical or legal advice. Precision, rounding and zero-denominator cases are surfaced rather than silently repaired. Keep a record of the assumptions when the result affects a decision.