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Transformer Calculator

Transformer Calculator

Select the parameters and enter their values. The calculator will immediately calculate voltage, current value, and other transformer-related terms.


Transformer Phase

Transformer Rating



Supervised/Unsupervised Location

% Impedance Without( % sign)

Primary Voltage


Secondary Voltage


Primary Winding

Secondary Winding

Primary Current

Secondary Current




co-efficient of eddy current

Thickness of the sheet

Maximum Flux Density


Hysteresis Constant

Number of Turns


Table of Content

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Make use of this free transformer calculator to instantly estimate voltage, load currents, various losses, and other related parameters.

Let’s move on towards ten calculations of the idea; and read; transformer.

What Is A Transformer?

In the field of electrical technology:

“A passive component that transfers electrical energy among various electrical circuits is called a transformer”

Transformer Symbol:
transformer symbol

Carefully watch the symbolic diagram of the transformer. Later on, we will elaborate it in detail for you as well. Another add is that our best transformer calculator will also let you estimate each and every element related to transformer functionality.

Types of Transformer:

Various types of transformer are there that are used for particular purposes in different fields. These include:

Step Up Transformer:

This kind of transformer has a secondary voltage greater than that of the primary voltage.

step up transformer

This transformer type is used in a locality or area where the voltage rating is very low and the public needs to use appliances that operate on higher voltages.

Step Down Transformer:

In this transformer, the primary voltage is higher than the secondary voltage.

step down transformer

Step down transformers are typically used in commercial or residential localities where consumers use different devices that operate on lower voltages. This online step down transformer calculator also signifies the working of this kind.

Single phase Transformer:

This transformer operates on only single phase power systems.

Three phase Transformer:

This transformer works on a supply of 3 phase power. You can consider this 3 phase transformer calculator to thoroughly investigate 3 phase power supplies distributors without any hurdle.

Current Transformer:

In a current transformer:

  • Only current is transmitted
  • Secondary winding ig more than that of the primary winding
  • The primary current is smaller than the secondary current
  • This transformer is always connected in a serial circuit

Voltage Transformer:

In a voltage transformer:

  • The overall voltage is decreased enough to run the home appliances
  • You should always connect a voltage transformer in parallel to the electrical circuit

Transformer Equations:

The basic transformer equation is given as follows and is also used to commence calculations by our online transformer calculator regarding transmission of voltages and currents:

$$ \frac {V_p}{V_s} = \frac {n_p}{n_s} $$


\(V_p\) = Primary Coil Voltage

\(V_s\) = Secondary Coil Voltage

\(n_p\) = Number of Turns on Primary Coil

\(n_s\) = Number of Turns on Secondary Coil

Transformer Size:

The sizeof the transformer is estimated on the basis of its rating power that could be either in volts, kilo volts, or mega volts. This free transformer sizing calculator also lets you understand the peak power transmission that could be carried out by a transformer.

In an electrical system, the transformer is the only element that is responsible for most of the issues. Whenever you feel there is any component behaving abnormally, try changing your transformer and it is 90% sure that the issue will be fixed at the moment.

Transformer Current:

You can determine the alternating currents for single and three phase transformers as follows:

Single Phase Transformer:

Full-Load Current (Amps)= kVA × 1000 / V

Three Phase Transformer:

Full-Load Current (Amps) = kVA × 1000 / (1.732 × V)

Turns Ratio:

The particular ratio of the primary coil winding to that of the secondary coil winding is called the turn ratio.

No doubt our best transformer turns ratio calculator figures out this specific ratio analysis in a couple of moments, but you can also determine this by subjecting to the expression below:

$$ Turns Ratio = \frac{N_1}{N_2} $$

You can also determine this particular element by subjecting to this free transformer turns ratio calculator.

For example:

If there is a 1:1 transformer, it means the number of coils on its primary and secondary windings are the same.

Various Transformer Losses:

It is a fact that every real system is not always perfect. The same is the case with the real transformer. When voltages are transferred to and from a transformer, it is confirmed that the receiving voltage would never be the same as it was applied. It is always less than the actual applied. This loss is due to the various factors that may include:

Eddy Currents Loss:

This loss is caused when a current is induced within the core of the ferromagnetic material just because of the electromagnetic induction. Now to avoid this kind of error in current transmission, you must use an iron core that consists of thin metallic sheets. You must keep in mind that these sheets must contain the highest resistivity.

Stray Loss:

The loss due to the flux leakage in the transformer is known as the stray loss. Not only this, but this loss also causes the production of the eddy currents on the magnetic core of the transformer. You can only be able to minimise the stray loss if and only if the leakage flux is controlled.

Dielectric Loss:

It occurs only in the insulating material of the electrical device. When it comes to the transformer, this material is present in the oil of it. The main reason for this loss is none other than quality loss of the dielectric material and the oil.

Core Loss or Iron Loss:

Rather than the eddy currents and hysteresis loss that are the causes of the core loss, the major cause is still the alternating flux. This loss is dependent on the voltage only.

Copper Loss:

This specific loss arises because of the ohmic resistance in both the windings of the transformer. When the current through the windings changes, it also causes a change in the copper loss of the device.

Ideal Transformer:

An ideal transformer is the one in which there is no power loss.

Power loss = P = Ip * Vp = Is * Vs.

The above equation represents that the electrical power in the primary coil and the secondary coil is the same.

Voltage In An Ideal Transformer:

You can determine the voltage for an ideal transformer by using the following expression:

Vs = Vp * Ns / Np

Current In An Ideal Transformer:

Get going to calculate the current by considering the transformer formula for ideal case below:

Is = Ip * Np / Ns

Transformer Amperage Chart:

Let’s have a look at couple of charts that describes the transformer sizes accordingly:

Single Phase Transformer:

Single Phase Transformers, Full Load Amperes (FLC)
KVA 120V 208V 240V 277V 480V 600V
.25 2.0 1.2 1. 0.9 0.5 0.4
.50 4.2 2.4 2.1 1.8 1.0 0.8
.75 6.3 3.6 3.1 2.7 1.6 1.3
1 8.3 4.8 4.2 3.6 2.1 1.7
1.5 12.5 7.2 6.2 5.4 3.1 2.5
2 16.7 9.6 8.3 7.2 4.2 3.3
3 25 14.4 12.5 10.8 6.2 5
5 41 24 20.8 18 10.4 8.3
7.5 62 36 31 27 15.6 12.5
10 83 48 41 36 20.8 16.7
15 125 72 62 54 31 25
25 206 120 104 90 52 41
37.5 312 180 156 135 76 62
50 416 240 208 180 104 83
75 625 340 312 270 156 125
100 833 480 416 361 208 166
167 1391 803 695 603 347 278

Three Phase Transformer:

Three Phase Transformers, Full Load Amperes (FLC)
KVA 208V 240V 480V 600V
3 8.3 7.2 3.6 2.9
6 16.6 14.4 7.2 5.8
9 25 21.6 10.8 8.6
15 41.7 36.1 18.0 14.4
30 83.4 72.3 36.1 28.9
45 124 108 54.2 43.4
75 208 180 90 72
112.5 312 270 135 108
150 416 360 180 144
225 624 541 270 216
300 832 721 360 288
500 1387 1202 601 481
750 2084 1806 903 723
1000 2779 2408 1204 963

All of the above mentioned ranges can also be cross verified by this free transformer amperage calculator in a fragment of seconds. How does it sound?

How To Analyze A Transformer?

What about resolving an example that will clarify your understanding of the transformer functionality? Let’s move ahead!

Example # 01:

There is a single phase transformer of size about 56kVA. Its primary voltage is 350 volts and secondary voltage is almost 673 volts. Considering the transformer tpo be the ideal one, calculate the turns ratio.


As the transformer is supposed to be ideal one:

Turns Ratio = N1 / N2 = V1 / V2 = (350 / 76) = 4.60

Example # 02:

Estimate the number of turns on the secondary coil with the following parameters of a current transformer given:

\(V_p\) = 30 volts

\(V_s\) = 70 volts

\(n_p\) = 5


We know that:

$$ \frac {V_p}{V_s} = \frac {n_p}{n_s} $$

Performing current transformer calculations:

$$ \frac {30}{70} = \frac {5}{n_s} $$

$$ n_s = \frac{5*70}{30} $$

$$ n_s = 11.66 $$

How Transformer Calculator Works?

This free transformer winding calculator allows you to know different stats regarding operation of a single phase or three phase transformer. Let’s understand how to use it and analyze this specific passive electric device.


  • First of all, tap on the drop down list and select whether you want to explore single phase or three phase transformer
  • Now move to the next list in which you will be provided with various options available. Select the parameters combination depending upon which you wish to calculate the unknown one.
  • After you do that, fetch all the required terms in their designate fields along with unit
  • At the end, tap ten calculate button

The best transformer KVA calculator does the following calculations:

  • Estimates primary and secondary voltages and currents
  • Estimates copper loss and Iron loss
  • Estimates Eddy current loss
  • Estimates Hysteresis loss
  • Estimates turns ratios for primary and secondary coils


Are transformers AC or DC?

Practically, no DC current can be passed through a transformer. But the DC voltage can be applied through it by creeping the AC voltage as well. Rest, this free transformer calculator amps takes a couple of seconds to figure out how many voltages it can carry at minimal transmission loss.

Why is DC not used in homes?

The direct current does not become zero. It remains the same and that is why it is strictly prohibited to use it for domestic purposes. For such purposes, alternating current is the preferred choice indeed.

What do you mean by the power factor?

Power factor is actually the ratio of the working power to the apparent power.

Why is rectifier used in transformer?

In a transformer, a rectifier behaves as a device that converts the alternating current into the direct current.

What is the primary difference between kW and kVA?

Power factor is the basic difference among both of these terms. Where the kW is the power of the real transformer, the kVA is considered the power factor of the apparent transformer.


Transformers are safety devices that are used worldwide to reduce or raise voltages according to the needs. Moreover, these electrical systematic devices are used to control current and voltages to be transmitted over long distances. This is why our best transformer calculator is designed to assist you people in understanding the various terms related to the functionality of a transformer.


From the source of Wikipedia:  Transformer, Principles, Leakage flux, Equivalent circuit, Polarity, Energy losses, Construction, Windings, Classification parameters, 

From the source of Khan Academy: Transformers

From the source of Lumen Learning: Transformers, Electrical Safety