Electrical calculator

Microstrip Impedance Calculator

Compute microstrip characteristic impedance Z0 from W/H/εr, or synthesize width for a target Z0 (zero-thickness IPC-2141 / Wadell–Hammerstad). Runs locally in your browser.

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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 · 3/3 declared partitions (z0, width, invalid-domain) · Matrix
Known limitations: No copper thickness correction; er>1
Core CVP does not include live graph, viewport, or pointer interaction.
Model: Microstrip Z0 or width from IPC-2141 / Hammerstad closed form.
Scope: Zero copper thickness; homogeneous dielectric; no mask
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: 3/3 property · digest dead067b2144
Legacy regression: 8/8 tests · Production surface contract 4/4
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: 2/2 golden · 3/3 CVP boundary · 2/2 invalid · 3/3 property · 1/1 cross-interface · 1/1 CVP contract · Manifest
Sources: IPC-2141A — Controlled Impedance Circuit Boards and High-Speed Logic Design — Microstrip impedance equations
Hammerstad / Jensen / Wadell microstrip models — Effective permittivity and Z0
Sources
Evidence: 2 legacy golden · 3 legacy boundary · legacy regression suite · 2/2 oracle-backed golden · 2/2 invalid · Artifact integrity PASS · CalculatorX electrical review
Semantic contract: PASS

Full verification

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

Formulas

Core equations used by this calculator.

Wide (W/H ≥ 1)Z0 = η0 / (√εeff · (u + 1.393 + 0.667·ln(u+1.444)))

Narrow (W/H < 1)Z0 = (60/√εeff)·ln(8/u + u/4)

iZero thickness; neglects copper roughness and soldermask. Synthesis and analysis can differ by ~0.2 Ω.

How to use

Choose analysis or synthesis

Analysis finds Z0 from geometry; synthesis targets a Z0 by solving width.

Enter dielectric height H and εr

H > 0 and εr ≥ 1 for the microstrip stack-up.

Enter W or target Z0

Provide the remaining known; read Z0 or the solved trace width.

Example calculations

Common configurations with formula and result.

≈50 Ω FR-4

W=0.37 mm · H=0.2 mm · εr=4.6

mode=z0

Z0 ≈ 50.20 Ω

Microstrip Impedance calculator specification

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

Calculation status

Engine tested 8/8 tests · Production surface contract 4/4
Supplemental domain review Internal · Pass · electrical-engineer · 2026-08-08
Named expert review Not performed
Calculation version 1.0.0

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

Definition: A microstrip is a strip conductor over a dielectric over a ground plane. This tool uses the IPC-2141 / Wadell–Hammerstad closed form for zero conductor thickness to find Z0 from W/H/εr or W from a target Z0.
What it calculates: Microstrip Z0 or width from IPC-2141 / Hammerstad closed form.
Inputs: mode: z0 | width
H_m > 0, er > 1
W_m > 0 (z0) or Z0_ohm > 0 (width)
Outputs: Z0_ohm
W_m
eps_eff
W_over_H
…
Formula: IPC-2141 / Wadell–Hammerstad zero-thickness microstrip
Assumptions: Zero copper thickness; homogeneous dielectric; no mask
Units: m, Ω
Boundary conditions: er ≤ 1 → ER_MUST_BE_GT_1
Bad mode → INVALID_MODE
Missing/≤0 → MISSING_REQUIRED_INPUT / VALUE_MUST_BE_POSITIVE
Example: W=0.37 mm, H=0.2 mm, er=4.6 → Z0≈50.20 Ω
Validation cases: 2 published on this page · 8/8 tests · Production surface contract 4/4 · View evidence
W=0.37mm, H=0.2mm, er=4.6 → Z0≈50.205
target 50 Ω → width → W≈0.370 mm
Sources: IPC-2141A — Controlled Impedance Circuit Boards and High-Speed Logic Design — Microstrip impedance equations
Supports: Closed-form Z0 vs W/H/εr
Hammerstad / Jensen / Wadell microstrip models — Effective permittivity and Z0
Supports: εeff and narrow/wide branch formulas
Last reviewed: 2026-08-08
Reviewed by: CalculatorX electrical review (electrical-engineer)
Calculation version: 1.0.0

Background

Interpretation and common distinctions.

Size microstrip controlled impedance with the IPC-2141 / Hammerstad closed form.

Default: W=0.37 mm · H=0.2 mm · εr=4.6 → Z0 ≈ 50.20 Ω.

Agent / API notes

Capability id: electrical.pcb.microstrip · tool id: pcb-microstrip · pin 1.0.0.

Errors: MISSING_REQUIRED_INPUT, INVALID_NUMBER, VALUE_MUST_BE_POSITIVE, INVALID_MODE, ER_MUST_BE_GT_1.

Other calculators in this family: PCB Differential Impedance Calculator, PCB Trace Thermal Calculator, PCB Trace Width Calculator (IPC-2221), Stripline Impedance Calculator, Via Current Capacity Calculator . Explore all PCB & Signal Integrity.

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Frequently asked questions

Key distinctions behind the calculation.

Is soldermask included?

No. This is bare microstrip with zero conductor thickness.

What if εr ≤ 1?

The API returns ER_MUST_BE_GT_1.