Math & Numbers
Convert between pH, [H+], pOH and [OH-], or compute pH from a strong acid/base concentration, including dilution.
ph-calculatorMath & Numbers
Calculate buffer solution pH with the Henderson-Hasselbalch equation, or find the acid/base ratio needed for a target pH.
ph-buffer-calculatorMath & Numbers
Calculate exact, cumulative, and upper-tail Poisson probabilities from an expected event rate
poisson-distribution-calculatorMath & Numbers
Convert a normal percentile, tail area, or central area into a standard normal z-score
percentile-to-z-score-calculatorMath & Numbers
Calculate permutations with or without repetition, plus circular arrangements, with formulas and optional steps
permutation-calculatorMath & Numbers
Calculate the perimeter of various geometric shapes
perimeter-calculatorMath & Numbers
Plot a normal-distribution bell curve as SVG with z-score markers, interval or tail-probability shading, and 68/95/99.7 standard-deviation bands.
normal-distribution-plotterMath & Numbers
Newton-Raphson iteration for f(x) = 0 with analytic or numeric derivative, full iteration table, and explicit convergence/divergence reporting.
newton-raphson-root-finderMath & Numbers
Forward, backward, and central finite differences for f′(x₀) plus the central second derivative, with optional per-method error against the exact derivative.
numerical-differentiationMath & Numbers
Composite Simpson's 1/3 rule for ∫f(x)dx (even n): node table with weights, integral estimate, optional exact value, O(h⁴) accuracy.
numerical-integration-simpsonMath & Numbers
Composite trapezoidal rule for ∫f(x)dx: node table, integral estimate, optional exact value and O(h²) error report.
numerical-integration-trapezoidMath & Numbers
a⁻¹ mod m via extended Euclid with Bézout coefficients, an optional step table, and an a × a⁻¹ ≡ 1 (mod m) verification; RSA-sized inputs supported.
modular-inverse-calculator