Admittance Calculator. Admittance is the measure of how easily an AC circuit allows current to flow — the inverse of impedance. Enter your circuit's Resistance (R) and Reactance (X) in ohms into the Admittance Calculator to get the Admittance Magnitude |Y| in siemens. Secondary outputs include Conductance (G), Susceptance (B), Impedance |Z|, and Phase Angle. Also try the calculate Damping Factor (ζ), System Type & Natural Frequency — Damping Factor.
Admittance (Y) is the measure of how easily alternating current flows through a circuit. It is the reciprocal of impedance (Y = 1/Z) and is measured in siemens (S). Admittance consists of conductance (real part) and susceptance (imaginary part). See also our LC Tank Circuit Calculator.
Admittance is calculated using Y = 1/Z = 1/(R + jX). The magnitude is |Y| = 1/√(R² + X²), conductance G = R/(R² + X²), and susceptance B = -X/(R² + X²), where R is resistance and X is reactance.
Conductance (G) is the real part of admittance that represents the resistive component's ability to conduct current. Susceptance (B) is the imaginary part that represents the reactive component's effect on current flow.
Admittance is measured in siemens (S), which is the reciprocal of ohms. One siemen equals one ampere per volt (1 S = 1 A/V). Both conductance and susceptance are also measured in siemens.
Positive reactance indicates inductive behavior (current lags voltage), while negative reactance indicates capacitive behavior (current leads voltage). The sign affects the susceptance component but not the admittance magnitude.
Admittance is particularly useful when analyzing parallel AC circuits, as admittances add directly in parallel combinations. It's also preferred in power system analysis and when working with Norton equivalent circuits.
As impedance approaches zero (short circuit condition), admittance approaches infinity. This represents maximum current flow capability. Conversely, when impedance is very high (open circuit), admittance approaches zero. You might also find our calculate Total Impedance |Z|, Inductive Reactance (XL) & Time Constant (τ) — RL Circuit useful.