Complex Number Magnitude |a+bi| = √(a²+b²). Real a Imag b |a+bi| 5 Step-by-step with your numbers: 1. Values used: 2. Real a = 3 3. Imag b = 4 4. |a+bi| = 5 Did we solve your problem today? 👍 Yes 👎 No Thanks for the feedback! Magnitude of complex number. FAQ Phase? θ = atan2(b,a). Related calculators Complex Conjugate Calculator a+bi → a−bi. Complex Number to Polar Form a+bi → r∠θ.