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Transformer Sizing Calculator

Ideal transformer: Vp/Vs=Np/Ns, currents, and VA = V·I. First-pass sizing. Runs locally in your browser.

Instant result
Result
—

Enter values to calculate.

Inputs—
Mode—
Formula—
Trust summary CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance
Input interpretation
Enter values to calculate.
Result
—
Assurance
Engineering
Declared partition coverage
PASS · 4/4 declared partitions (ratio, va, current, invalid-domain) · Matrix
Known limitations
  • Ideal lossless transformer; no magnetizing current
  • Core CVP does not include live graph, viewport, or pointer interaction.
Model
Ideal transformer ratio, currents, or VA rating.
Scope
Ideal lossless single-phase
Verification
Engine tested · Source checked · v1.0.0 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Versions
Calculation 1.0.0 · CVP protocol 1.0.0-proposed
CVP identity
2/2 property · digest a4a1bbe624c5
Legacy regression
7/7 tests · Production surface contract 3/3
Reference
O1 model · O2 expected_values · O2 numerical_behavior
Interfaces
PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session.
Supplemental domain review
Internal · Pass · electrical-engineer
Named expert review
Not performed
CVP suite
3/3 golden · 2/2 CVP boundary · 1/1 invalid · 2/2 property · 1/1 cross-interface · 1/1 CVP contract · Manifest
Sources
  • IEC 60076 — Power transformers (concepts) — Ideal transformer ratios
  • Chapman — Electric Machinery Fundamentals — Ideal transformer
Sources
Evidence
3 legacy golden · 2 legacy boundary · legacy regression suite · 3/3 oracle-backed golden · 1/1 invalid · Artifact integrity PASS · CalculatorX electrical review
This calculator CURRENT · Public schema 1.0.0 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓
Semantic contract
PASS
Full verification

Manifest identity, reference classes, interfaces, suite, and production records.

Formulas

Core equations used by this calculator.

Voltage / turnsVp/Vs = Np/Ns
CurrentIp/Is = Ns/Np
VAS = V·I
iIdeal, lossless, single-phase. Not for regulation, inrush, or unbalanced 3φ.

How to use

1

Choose ratio, current, or VA mode

Ratio uses turns/voltages; current uses Ip/Is; VA uses V·I style sizing.

2

Enter the known voltages, turns, or currents

All used values must be greater than zero.

3

Read the solved ratio, current, or apparent power

Ideal transformer: Vp/Vs = Np/Ns and Vp·Ip ≈ Vs·Is.

Example calculations

Common configurations with formula and result.

ϟ

10:1 step-down

240 V → 24 V · Np=100

Ns=Np·Vs/Vp
Ns=10

Transformer Sizing calculator specification

Version 1.0.0 · Engine tested · Supplemental domain review · Internal · 2026-08-08

Calculation status

Review policy · Evidence · Reviewed by CalculatorX electrical review (electrical-engineer)

Definition
An ideal transformer scales voltages by turns ratio Vp/Vs=Np/Ns and currents inversely. Apparent power S=V·I is conserved (neglecting losses).
What it calculates
Ideal transformer ratio, currents, or VA rating.
Inputs
  • mode ratio|current|va
  • Vp,Vs,Np,Ns / Ip,Is / V,I
Outputs
  • turns_ratio / Ip,Is / S_VA
Formula
Vp/Vs=Np/Ns; S=V·I
Assumptions
  • Ideal lossless single-phase
Units
  • V, A, turns, VA
Boundary conditions
  • <3 of Vp,Vs,Np,Ns → NEEDS_THREE_INPUTS
  • V,I ≤0 as applicable → VALUE_MUST_BE_POSITIVE / NON_NEGATIVE
Example
Vp=240,Vs=24,Np=100 → Ns=10
Validation cases

1 published on this page · 7/7 tests · Production surface contract 3/3 · View evidence

  • ratio Vp=240 Vs=24 Np=100 → Ns=10
Sources
  • IEC 60076 — Power transformers (concepts) — Ideal transformer ratios
    Supports: Voltage/turns and VA basics
  • Chapman — Electric Machinery Fundamentals — Ideal transformer
    Supports: Vp/Vs = Np/Ns and VA conservation
Last reviewed
2026-08-08
Reviewed by
CalculatorX electrical review (electrical-engineer)
Calculation version
1.0.0

Background

Interpretation and common distinctions.

Ideal transformer sizing.

Supported and not supported

Supported — Ratio · current · VA · API electrical.transformer_sizing

Not supported — Regulation curves, inrush, unbalanced 3φ

Agent / API notes

Capability id: electrical.transformer_sizing · tool id: transformer-sizing · pin 1.0.0.

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Frequently asked questions

Key distinctions behind the calculation.

Is efficiency included?

No — ideal transformer. Real efficiency and regulation need nameplate data.