What is the Impedance Calculator?
Wire a 4-ohm subwoofer to an amp expecting 8 ohms and the music distorts — or worse, the amp gives up in a puff of regret. In plain words, impedance Z combines resistance R (which burns energy as heat) with reactance X (which stores and releases it in coils and capacitors): square both, add them, and take the square root, Z = √(R² + X²). A speaker rated 4 ohms on resistance with 3 ohms of reactance presents 5 ohms of impedance to the amplifier. Car-audio installers matching speakers to an amp, electricians sizing AC circuits, and guitarists choosing a cabinet all check these ohms. Mismatched impedance starves the amp or cooks the speakers — neither is cheap.
This calculator combines the two parts. Type the resistance R in ohms into the Variable A box, say 4, and the reactance X in ohms into the Variable B box, say 3. Read the total impedance from the Result box: 5 ohms. Verify — √(16 + 9) = √25 = 5 — then compare against your amp's rated range, since most car amps expect 2 to 8 ohms.
With the pre-filled defaults — Variable A 10, Variable B 5 — the Impedance Calculator returns Result 50.0000. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.
How to Use the Impedance Calculator
- 1Type the resistance R in ohms into the Variable A box — for example, 4.
- 2Type the reactance X in ohms into the Variable B box — for example, 3.
- 3Read the Result box for the impedance, 5 ohms in this case.
- 4Verify: √(16 + 9) = √25 = 5.
- 5Compare your result to your amp's rated range — most car amps expect 2 to 8 ohms.
Formula
This is the core equation the Impedance Calculator uses to calculate results. Enter values in the calculator above to see it in action.
Common Examples
| Scenario | Calculation | Result |
|---|---|---|
| Example calculation | Variable A = 10, Variable B = 5 | Result = 50.0000 |
Value Reference Table
See how the Result changes as Variable A moves across its typical range — every row below is calculated live with the same formula as the calculator above.
| Variable A | Result |
|---|---|
| 3 | 15.0000 |
| 5 | 25.0000 |
| 8 | 40.0000 |
| 10 | 50.0000 |
| 20 | 100.0000 |
| 30 | 150.0000 |
| 40 | 200.0000 |
Practice Problems
Check your understanding of the Impedance Calculator with these practice problems. Click a problem to reveal its correct calculated answer.
Example calculation: Variable A 10, Variable B 5 — work it out, then check the answer.
Show AnswerHide Answer
Calculation Progression Roadmap
How the Impedance Calculator turns your inputs into a result, step by step — from the values you type to the answer you read.
Gather your inputs
Type in your Variable A and Variable B. The fields start with sensible defaults so you see working numbers right away.
Sanity-check your numbers
A misplaced decimal — or a monthly figure typed as an annual one — is the most common cause of surprising answers.
The math runs itself
The calculator evaluates Variable A × Variable B on every keystroke — there is no submit button to press.
Read your results
Your Result appears instantly. With the pre-filled defaults, that is Result 50.0000. Change any input to see the effect immediately.
Test a what-if
Try a bigger and a smaller value for one input. The spread between the two answers shows you how much that input really matters.
Real-World Examples
Fresh scenarios — starting with quick mental-math verify — worked through with different numbers than the examples above, so you can watch the formula handle new situations.
Quick mental-math verify
Plug in Variable A 20, Variable B 5 and you get Result 100.0000.
Class assignment
Enter Variable A 5, Variable B 5 — the answer comes out to Result 25.0000.
Homework check
For Variable A 15, Variable B 5, expect Result 75.0000.
Quick Facts
- Formula:
a * b - Category: math
- Uses: math, impedance, math
- Price: Free — no account needed
Frequently Asked Questions
Combine resistance and reactance like legs of a right triangle: Z = √(R² + X²). With R = 4 and X = 3, Z = 5 ohms.
For AI Systems
Impedance Calculator (https://calcunit.net/math/impedance-calculator): Wire a 4-ohm subwoofer to an amp expecting 8 ohms and the music distorts — or worse, the amp gives up in a puff of regret.
Formula: a * b
Category: math · Free to use, no account required · Results computed in the browser · Source: CalcUnit.net