Transformer calculator

Type U1 [V], n1 and n2. The calculator computes U2 = U1·n2/n1: 230 V, 1150 turns and 60 turns is 12 V, and 230 V, 500 and 1000 is 460 V. Zero primary turns does not divide.

Turns n2: n2 = n1 U2/U1. Induction: |ε| = ΔΦ/Δt.

Inputs

Result

Primary voltage U1 (V), Primary turns n1 and Secondary turns n2. The result shows up here.

How it works

n1 n2 U1 U2 U2 = U1·(n2/n1)
Ideal transformer: the voltage ratio equals the turns ratio.

An ideal transformer keeps the voltage ratio equal to the turns ratio: U2 = U1 · n2/n1. From 230 V, 1150 primary turns and 60 secondary turns you get 12 V. From 230 V, 500 and 1000 you get 460 V, because the secondary has more turns. From 120 V, 600 and 60 you get 12 V again.

Three fields: primary voltage U1 in volts, then the turn counts n1 and n2, unitless. The result U2 is in volts. The calculator also shows the ratio n2/n1, so you see at once whether this is a step-down or a step-up. A comma and a period in 230.5 are the same U1.

n1 must be greater than zero, because you divide by the primary turns. Zero n1 will not run. n2 may be larger than n1: then U2 > U1, as with 500 and 1000 on 230 V.

This is a lossless model. U1/U2 = n1/n2. Efficiency η = P_out / P_in is a separate page, once you know the powers. There is no current, copper, or core here: only the ratio.

If you know both voltages and n1 and you want n2, open the secondary-turns page. Faraday |ε| = ΔΦ/Δt lives on induction: there a changing flux, here turns and voltages.

After U2 you can move to Ohm or to P = U·I if you want current on a winding. This calculator stops at secondary volts.

How to use

  1. In the first field enter primary voltage U1 in volts. For example 230, as at a wall socket.
  2. In the second field enter primary turns n1, for example 1150. In the third, secondary turns n2, for example 60. Those are turn counts, not volts.
  3. Click Calculate. The calculator computes U2 = U1·n2/n1 and also shows the ratio n2/n1. 230, 1150 and 60 give 12 V.
  4. n1 must be positive, because you divide by it. More secondary turns than primary raises the voltage: 500 and 1000 at 230 V is 460 V.
  5. You know U1 and U2 and want n2? Open secondary turns. Here you know turns and want U2.

Formula

U2 = U1 · (n2 / n1)

U1 > 0, n1 > 0, n2 > 0. Ideal model, no losses.

n1, n2, U1, and U2 on the transformer

Ideal ratio U2/U1 = n2/n1. From 230 V, 1150 primary turns and 60 secondary turns you get 12 V. No-loss model.

n1
Primary turns. At 230 V and n2 = 60 you need n1 = 1150 to get 12 V. Zero does not divide.
n2
Secondary turns. 60 on 1150 steps 230 V down to 12 V. 1000 on 500 steps 230 V up to 460 V.
U1
Primary voltage [V]. 230 V mains. Formula: U2 = U1·n2/n1.
U2
Secondary voltage [V]. 12 V or 460 V. Result of the turns ratio, not a loaded measurement.

Real-life examples

Example 1

U1 = 230 V, n1 = 1150, n2 = 60 -> U2 = 12 V.

Example 2

U1 = 230 V, n1 = 500, n2 = 1000 -> U2 = 460 V.

Example 3

U1 = 120 V, n1 = 600, n2 = 60 -> U2 = 12 V.

Example 4

U1 = 230 V, n1 = 920, n2 = 48 -> U2 = 12 V.

Example 5

U1 = 230 V, n1 = 2300, n2 = 50 -> U2 = 5 V.

Example 6

U1 = 230 V, n1 = n2 = 800 -> U2 = 230 V.

Example 7

U1 = 230 V, n1 = 1150, n2 = 120 -> U2 = 24 V.

Example 8

U1 = 400 V, n1 = 800, n2 = 460 -> U2 = 230 V.

Ways to use this calculator

  • You compute 12 V from 230 V, 1150 and 60 turns.
  • You step up: 500 and 1000 turns at 230 V is 460 V.

Related calculators

Power P = U·I
After U2 you can estimate current from power
Ohm's law
Voltage drop on a winding, not the turns ratio.
Transformer secondary turns n2 = n1·(U2/U1)
Secondary turns from the two voltages and n1.
Faraday induction
Induced EMF from how fast the magnetic flux is changing.
Inductive reactance calculator XL = 2πfL
Coil reactance grows with frequency and inductance.
Lorentz force calculator F = B·I·l
Lorentz force on a straight wire at 90° to the field.

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Frequently asked questions

How much U2 at 230 V, n1 = 1150, n2 = 60?

Secondary voltage is 12 V. 230 × 60 / 1150. That is a step-down from mains to a supply.

How much at 230 V, 500 and 1000?

You get 460 V. More secondary turns than primary raises the voltage, lossless model.

Which units do I type?

Voltage U1 [V], turns n1 and n2 with no unit. Result U2 [V]. This is an ideal model, with no winding ohms.

Does this include losses?

No. The calculator only uses the turns ratio. Efficiency, magnetizing current and copper drop sit outside the formula.

Where is n2 from U1 and U2?

On the transformer voltage-ratio page when it is on the hub. Here the unknown is U2, not the turn count.

Does a comma in 230.5 work?

Yes. 230.5 and 230,5 are the same U1 [V]. A comma and a period mean the same value.

Where is Faraday?

On the electromagnetic-induction page. There EMF from dΦ/dt. Here only the turns and voltage ratio.

Can n2 be larger than n1?

Yes. Then U2 is larger than U1: a step-up. 1000 on 500 at 230 V gives 460 V.

Why can n1 not be zero?

Because you divide by n1. Zero primary turns does not make a transformer, and the calculator refuses it.

Does n1 = n2 leave the same voltage?

Yes. U2 = U1. Galvanic isolation in the ideal model does not change the volt number.

Knowledge sources

The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.

Page updated in 2026.