Math & Numbers
Convert between different energy units (joules, calories, kilowatt-hours, BTU, etc.)
energy-converterFinance
Check if a string is an Ethereum address. Does not validate address checksums.
eth-address-validatorFinance
Calculate dividend income, yield, and total returns from stock investments
dividend-calculatorCalculator
Calculate probabilities for dice rolls and combinations
dice-probabilityMath & Numbers
Calculate derivatives of common functions
derivative-calculatorMath & Numbers
Compute radial steady-state heat conduction through a single-layer cylindrical wall (Fourier's law in cylindrical coordinates): radial heat flow rate Q = 2π·k·L·ΔT/ln(r₂/r₁) (W), inner-surface heat flux q_inner = Q/(2π·r₁·L) (W/m²), outer-surface heat flux q_outer = Q/(2π·r₂·L) (W/m²), and cylindrical thermal resistance R = ln(r₂/r₁)/(2π·k·L) (K/W). k is the thermal conductivity (W/(m·K)); L the cylinder length; r₁ the inner radius, r₂ the outer radius (must have r₂ > r₁ > 0); ΔT the temperature difference (K; a °C difference equals a K difference, a °F difference is converted by ×5/9). ΔT may be negative (indicating reverse heat flow), but k, L, r₁ and r₂ must be positive. Length and radius in m/cm/mm.
cylinder-radial-conductionMath & Numbers
Compute the back-EMF and electromagnetic torque of a DC motor from its machine constant: E=k·ω, T=k·I. In SI units the back-EMF constant equals the torque constant (k_e=k_t=k, V·s/rad=N·m/A). Also returns the mechanical (air-gap) power P=T·ω=E·I. Speed accepted in rad/s or RPM.
dc-motor-back-emfFinance
Convert an amount between currencies using live exchange rates from a free, no-key API (open.er-api.com). Supports 160+ world currencies. Shows the converted amount, the exchange rate used, a comparison table against popular currencies, and the rate update timestamp.
currency-exchangeFinance
General-purpose debt payoff planner comparing avalanche, snowball, and minimum-only strategies. Enter debts as 'name, balance, APR%, minPayment $' per line plus an extra monthly payment. Shows payoff time, total interest, savings, balance decline curves, and a per-debt repayment detail table.
debt-payoff-calculatorMath & Numbers
Convert between ratios and decibels (10·log power, 20·log amplitude), and across absolute units dBm/dBW/dBV/dBu/dBFS/SIL
decibel-calculatorMath & Numbers
Convert days to hours with configurable decimal precision
days-to-hoursMath & Numbers
Convert whole days to exact calendar months from a specified start year and month
days-to-months