What is the transformer turns ratio?

The turns ratio N₁/N₂ determines voltage and current transformation. V₂ = V₁ × (N₂/N₁) and I₂ = I₁ × (N₁/N₂). A 120V to 12V step-down transformer has N₁/N₂ = 10.

What is impedance reflection in a transformer?

A load impedance Z_load connected to the secondary appears as Z_primary = (N₁/N₂)² × Z_load at the primary. This is used in audio amplifiers to match a high-impedance tube amplifier to a low-impedance speaker.

What are copper and core losses?

Copper losses (I²R) occur in the winding resistance. Core losses include eddy current losses (induced circulating currents in the iron) and hysteresis losses (energy to magnetize/demagnetize the core each cycle). Together they reduce efficiency below 100%.

What is a typical transformer efficiency?

Large power transformers (>100 kVA) can reach 98–99.5% efficiency. Small signal transformers may be 85–95%. Efficiency is highest at the rated load.

Transformer Turns Ratio Calculator

Calculate secondary voltage, current, and impedance for power transformers. Enter turns ratio N₁/N₂, primary voltage, and current. Covers step-up, step-down, efficiency, and impedance reflection.

Primary Turns N₁

Secondary Turns N₂

Primary Voltage V₁ (V)

Secondary Voltage V₂ (V)

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Turns Ratio N₁:N₂ —

Transformer Type —

Extended More scenarios, charts & detailed breakdown ▾

Primary Turns N₁

Secondary Turns N₂

Primary Voltage V₁ (V)

Primary Current I₁ (A)

Secondary Voltage V₂ (V)

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Secondary Current I₂ (A) —

Turns Ratio N₁/N₂ —

Professional Full parameters & maximum detail ▾

Primary Turns N₁

Secondary Turns N₂

Primary Voltage V₁ (V)

Primary Current I₁ (A)

Efficiency η (%)

Load Impedance Z_load (Ω)

Secondary Voltage V₂ (V)

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Secondary Current I₂ (A) —

Reflected Impedance Z_primary (Ω) —

Power Loss (W) —

Copper Loss Estimate (W) —

How to Use This Calculator

Enter primary turns N₁, secondary turns N₂, and primary voltage V₁.
The simple tier gives secondary voltage V₂ and transformer type.
Use Extended tabs to find required turns from voltages or analyze efficiency.
Professional mode adds impedance reflection and loss breakdown.

Formula

V₂ = V₁ × (N₂/N₁) | I₂ = I₁ × (N₁/N₂)
Z_primary = (N₁/N₂)² × Z_load
P₂ = P₁ × η | P_loss = P₁ × (1 − η)

Example

N₁=1000, N₂=100, V₁=120V → V₂ = 120 × (100/1000) = 12 V. I₁=2A → I₂ = 2 × 10 = 20 A.

Frequently Asked Questions

The turns ratio N₁/N₂ determines voltage and current transformation. V₂ = V₁ × (N₂/N₁) and I₂ = I₁ × (N₁/N₂). A 120V to 12V step-down transformer has N₁/N₂ = 10.
A load impedance Z_load connected to the secondary appears as Z_primary = (N₁/N₂)² × Z_load at the primary. This is used in audio amplifiers to match a high-impedance tube amplifier to a low-impedance speaker.
Copper losses (I²R) occur in the winding resistance. Core losses include eddy current losses (induced circulating currents in the iron) and hysteresis losses (energy to magnetize/demagnetize the core each cycle). Together they reduce efficiency below 100%.
Large power transformers (>100 kVA) can reach 98–99.5% efficiency. Small signal transformers may be 85–95%. Efficiency is highest at the rated load.

Related Calculators

Sources & References (5) ▾

HyperPhysics – Transformer — Georgia State University
IEEE C57.12.00 – General Requirements for Transformers — IEEE
NEMA TR 1 – Transformers, Regulators and Reactors — NEMA
OpenStax University Physics Vol. 2 Ch. 13 – Electromagnetic Induction — OpenStax
MIT OCW 6.013 – Electromagnetics and Applications — MIT OpenCourseWare