Transformer Calculator
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What problem does this solve? Designers and engineers need to quickly determine transformer parameters (turns ratio, secondary voltage/current, power) for power supplies, voltage conversion, and electrical systems. This calculator provides instant, accurate results using the ideal transformer equations.
Find Turns Ratio
Find Secondary Voltage
Find Secondary Current
Power Transfer
V
kV
V
kV
A
mA
A
mA
Turns ratio n = Vp / Vs = Is / Ip (ideal). Enter any two related values.
Common Transformers (Reference)
Presets fill primary/secondary voltages (for reference). Adjust as needed.
Turns Ratio (n)
0.00
n = Vp / Vs = Is / Ip
Formula Used
n = Vp / Vs
Secondary Values
-
Power (VA)
-
What Problem Does This Calculator Solve?
Transformers are essential components in electrical systems for stepping voltage up or down. Engineers, electricians, and hobbyists often need to quickly determine:
- Turns ratio – to understand the relationship between primary and secondary windings.
- Secondary voltage – when designing power supplies or adapting voltages.
- Secondary current – to ensure wiring and components can handle the load.
- Power rating (VA) – to select the correct transformer for an application.
This calculator eliminates manual calculations and reduces errors, providing instant results for ideal transformers. Whether you're designing a DC power supply, sizing a transformer for a motor, or simply verifying a circuit, this tool gives you the answers you need.
How to Use This Transformer Calculator
- Select the calculation mode from the tabs above: Turns Ratio, Secondary Voltage, Secondary Current, or Power Transfer.
- Enter the known values in the appropriate fields. Use the unit buttons to switch between V/kV or A/mA as needed.
- If you have optional values (like primary current when finding turns ratio), you can enter them to get additional derived results (secondary current/power).
- Click Calculate – the result will appear with the formula used, secondary values, and apparent power.
- Use the preset dropdown to load typical transformer examples for reference (values are filled, but you can modify them).
Note: The calculator assumes an ideal transformer (no losses). For real-world applications, consider efficiency (typically 80–98%).
Ideal Transformer Equations
Vp / Vs = Np / Ns = Is / Ip
Vp × Ip = Vs × Is
Np, Ns: number of turns (primary, secondary)
Vp, Vs: primary and secondary voltage
Ip, Is: primary and secondary current
Power: input power = output power (ideal, no losses)
People Also Ask
🤔 How do I calculate turns ratio of a transformer?
Turns ratio n = Np/Ns = Vp/Vs = Is/Ip. If you know any two related values, you can find the ratio.
🔍 What is the difference between step-up and step-down transformer?
Step-up increases voltage (n < 1), step-down decreases voltage (n > 1). Our calculator works for both.
⚡ How to find secondary current from primary current?
Is = Ip × (Np/Ns) = Ip × n. For step-down (n>1), secondary current is higher.
📏 Does a transformer change power?
In an ideal transformer, power in = power out (neglecting losses). Real transformers have efficiency <100%.
🎯 What is the VA rating of a transformer?
VA = V × I (apparent power). It indicates the maximum power the transformer can deliver.
🔥 Real-world applications?
Power distribution, electronics power supplies, impedance matching, isolation.
How Transformers Work
A transformer transfers electrical energy between circuits through electromagnetic induction. It consists of two or more coils wound on a common core. The ratio of turns determines the voltage and current transformation.
Key Formulas
- Voltage ratio: Vp / Vs = Np / Ns
- Current ratio: Ip / Is = Ns / Np
- Power (ideal): Vp × Ip = Vs × Is
Typical Transformer Examples
| Type | Primary | Secondary | Turns Ratio (Np/Ns) |
|---|---|---|---|
| Step-down (wall adapter) | 230 V | 12 V | 19.17 |
| Step-down (low voltage) | 230 V | 24 V | 9.58 |
| Step-up (inverter) | 12 V | 230 V | 0.052 |
| Distribution transformer | 11 kV | 415 V | 26.5 |
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Common Questions
Can I use this calculator for three-phase transformers?
This calculator assumes single-phase ideal transformers. For three-phase, line and phase voltages must be considered separately.
What about transformer efficiency?
Our calculator assumes 100% efficiency (ideal). Real transformers have losses (copper, core). Output power = efficiency × input power.