BPM to milliseconds for note values, dotted and triplet delay times; or average tap intervals into a steady BPM.

Spell a scale or mode on any root: major, minor, modes, harmonic and melodic minor, pentatonic, blues, whole tone.

Roman numeral analysis of a chord progression in a key: numerals, inversions, borrowed chords, secondary dominants.

Note name (C#4, Bb3) or MIDI number to MIDI, frequency in Hz and wavelength, with adjustable A4 reference pitch.

Key signature (sharps or flats), circle-of-fifths neighbours, relative and parallel keys for any major or minor key.

Interval between two notes (quality, number, semitones) or the note a given interval above or below a note.

Required sample size for a survey (margin of error, optional finite population) or an A/B test (baseline, lift, power).

Primality test and prime factorization of integers up to 10^19, with divisor count, divisor sum, Euler totient and number type.

Transpose a chord progression by semitones or from one key to another, with spelling that fits the target key.

Compound annual growth rate from start and end values over years, or dates, or periods. Arithmetic on your numbers, not advice.

Bayes' theorem: posterior probability from a prior, sensitivity and false-positive rate, with natural frequencies and odds form.

Kelly criterion fraction for a stated win probability and payoff, with growth rate and overbet threshold. NOT advice.

Maximum drawdown of a price or return series you supply, with peak, trough and recovery indices or dates.

Rolling mean return and rolling annualized volatility over a window, from a price or return series you supply.

Simple and log returns from a price series you supply, with cumulative return. Educational arithmetic, not advice.

Equity-curve summary of a price or return series you supply: CAGR, volatility, Sharpe, drawdown, best and worst period.

Annualized volatility (sample standard deviation of returns) from a price or return series you supply. Not advice.

Sharpe and Sortino ratios on a price or return series you supply, with your risk-free rate. Not advice.

Correlation, beta, R-squared and alpha of one return or price series against another you supply. Not advice.

ILLUSTRATIVE historical and parametric Value-at-Risk and expected shortfall from a return series you supply. Not advice.