11 electronics design calculators.
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Decode a 4, 5 or 6-band resistor into resistance, tolerance and temp coefficient, or look up bands for a value.
Find the series resistor for an LED from supply, forward voltage and current, with the nearest E12 value.
Total resistance for any number of resistors in series (sum) and in parallel (reciprocal) at once.
Output voltage of a resistive divider, or solve for a resistor to hit a target, plus the divider current.
Enter any 2 of V, I, R, P → get the other two. V=I·R, P=V·I.
Frequency, period and duty cycle for a 555 in astable mode, or pulse width in monostable, from R1, R2, C.
Decode the 3-digit code on a ceramic capacitor (like 104 or 223) into pF, nF and µF, with tolerance.
The -3dB cutoff of a first-order RC low-pass or high-pass filter, or solve for R or C from a target.
Resonant frequency of an LC tank circuit from L and C, or solve for L or C to tune to a target.
Convert a power or voltage ratio to decibels and back (10·log for power, 20·log for voltage).
Estimate runtime from battery capacity (mAh / Ah) and device current draw, with a derating factor.
A set of electronics calculators for hobbyists, makers and engineers: decode resistor colour bands and capacitor codes, size an LED series resistor, design a 555 timer, work out RC and LC filter frequencies, combine resistors, convert decibels and estimate battery life. Pure-math, runs entirely in your browser.
They use the standard closed-form formulas (Ohms law, the 555 timer equations, the RC and LC frequency formulas, and the resistor and capacitor codes). They are exact for the ideal models; real components vary within their tolerance band.
No. Every calculator runs entirely in your browser with no download, sign-up, or data leaving your device.
Resistor colour code, LED series resistor, parallel and series resistors, voltage divider, Ohms law, 555 timer, capacitor code, RC filter, LC resonance, decibel converter and battery life.