Transformer Calculator

Calculate ideal transformer voltage and current ratios from winding turns. Enter your own values below to see ideal secondary voltage and check the method behind it.

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Your inputs

Change the example values to match your situation.

Your result

Let’s work it out.

Fill in your inputs and select Calculate.
Your result and breakdown will appear here.

How this calculator works

Ideal transformer: Vs/Vp = Ns/Np; Is/Ip = Np/Ns. Losses and regulation are excluded.

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What is Transformer Calculator?

Transformer Calculator helps you calculate ideal transformer voltage and current ratios from winding turns.

The main result is ideal secondary voltage, with a breakdown of ideal secondary current and turns ratio (primary/secondary). The formula, example and assumptions below explain how to interpret it.

How to use Transformer Calculator

Use the example to get familiar with the form, then enter your own figures. Any rates in the example are illustrative. Check the field labels and units before calculating.

  1. Gather primary voltage (V), primary turns, secondary turns and primary current (A). Use values from the same situation or reporting period.
  2. Replace the example primary voltage with your own value, then complete the other fields. Check the displayed units.
  3. Select Calculate and read ideal secondary voltage with its result breakdown. Change one input and calculate again to compare a second scenario. Reset restores the original example.
  • Enter primary voltage in V, at least 0. Decimals are accepted.
  • Enter primary turns, at least 1 and at most 10000. Use a whole number.
  • Enter secondary turns, at least 1 and at most 10000. Use a whole number.
  • Enter primary current in A, at least 0. Decimals are accepted.

Transformer Calculator: a worked example

With the inputs below, the result is 23 V (ideal secondary voltage). Follow the example, then replace these illustrative values with your own.

Example inputs and output
Input or outputExample value
Primary voltage (V)230 V
Primary turns1,000
Secondary turns100
Primary current (A)1 A
Ideal secondary voltage23 V
Ideal secondary current10 A
Turns ratio (primary/secondary)10

Understanding the Transformer result

Read ideal secondary voltage alongside ideal secondary current and turns ratio (primary/secondary). These describe different parts of the same calculation.

Displayed results use a readable number of decimal places. When checking a result by hand, keep extra precision until the last step. To compare scenarios, change one input at a time and keep the others fixed.

  • Example Ideal secondary current: 10 A
  • Example Turns ratio (primary/secondary): 10

Transformer Calculator: assumptions and common mistakes

A useful estimate starts with the right inputs. Check the following assumptions and limits before applying the result to your situation.

  • DC, single-phase and three-phase calculations use different relationships. Equipment selection also depends on installation conditions and applicable standards.

For wider guidance, visit Bureau of Indian Standards. The formula and scope of this specific tool are stated on this page.

Transformer Calculator FAQs

What does Transformer Calculator calculate?

Transformer Calculator helps you calculate ideal transformer voltage and current ratios from winding turns. Its main output is ideal secondary voltage in V.

What inputs do I need for Transformer Calculator?

You need primary voltage (V), primary turns, secondary turns and primary current (A). Use the field labels and units to match your figures to the formula.

Which formula does Transformer Calculator use?

Ideal transformer: Vs/Vp = Ns/Np; Is/Ip = Np/Ns. Losses and regulation are excluded.

What is a worked example for Transformer Calculator?

Example inputs: Primary voltage: 230 V; Primary turns: 1,000; Secondary turns: 100; Primary current: 1 A. The result is 23 V (ideal secondary voltage).

How should I enter primary voltage?

Enter primary voltage in V, at least 0. Decimals are accepted.

How do I choose primary turns?

Enter primary turns, at least 1 and at most 10000. Use a whole number. The example uses 1,000; replace it if your circumstances differ.

How should I read ideal secondary voltage?

Read ideal secondary voltage alongside ideal secondary current and turns ratio (primary/secondary). These describe different parts of the same calculation.

Why might my Transformer Calculator result differ from my records?

DC, single-phase and three-phase calculations use different relationships. Equipment selection also depends on installation conditions and applicable standards. Differences in entered values, units or rounding can also change the comparison.

Can I compare two scenarios in Transformer Calculator?

Yes. Note your first ideal secondary voltage, change primary voltage or another input, and select Calculate again. Editing a field clears the old result so it is not mistaken for a new calculation.

Is Transformer Calculator free, and where are my inputs calculated?

This calculator is free to use without signing in. Its formula runs in your browser; calculator inputs are not sent to a calculation API. The inputs reset to the example values when you reset the form or start a fresh page.