Engineering calculator

Guard Band Calculator

Q: Is this an ILAC G8 decision rule?

No. This page uses GB=k·u and optional A_USL=USL−GB, A_LSL=LSL+GB. It does not compute consumer/producer risk or a specific ILAC G8 / JCGM 106 rule.

Q: How is this different from Cp/Cpk?

Cp/Cpk compares a process σ to the specification window. A guard band shrinks the acceptance window by k·u. Use both if you need capability and a measurement decision rule.

Q: Where does this run?

Locally in the browser by default. REST and MCP call the same metrology-engine process ops.

Compute a simple guard band GB=k·u and optional acceptance limits USL−GB and LSL+GB. Runs locally. Not ILAC G8 risk-based decision rules.

Instant result

Result

—

Enter values to calculate.

Inputs—

Mode—

Formula—

Trust summary CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance · Simple guard band GB=k·u (k default 2) and optional A_USL/A_LSL + O3 mpmath tabulated GB.

Input interpretation: Enter values to calculate.
Result: —
Verified scope: Simple guard band GB=k·u (k default 2) and optional A_USL/A_LSL + O3 mpmath tabulated GB.
Assurance: Engineering
Declared partition coverage: PASS · 6/6 declared partitions (default-k, explicit-k, two-sided, usl-only, lsl-only, invalid-domain) · Matrix
Deferred: Not ILAC G8 / JCGM 106 consumer-producer risk tables, not Cp/Cpk, not Monte Carlo, and not a standalone Combined/Expanded page.
Numerical scope: O2: GB=k·u and optional acceptance limits vs separate-module identities (≤2 ULP). Not ILAC G8 risk, not Cp/Cpk, not Monte Carlo. ≤2 ULP vs O3 applies only to the published tabulated GB vectors (default k, explicit k, two-sided, USL-only, LSL-only, u=0). It is not a whole-domain guarantee and does not cover ILAC G8 risk or Cp/Cpk.
Known limitations: Core CVP does not include live graph, viewport, or pointer interaction.
Model: Simple guard band GB=k·u and optional acceptance limits.
Scope: GB = k·u with k default 2
Verification: Engine tested · Source checked · v1.0.0 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance · Simple guard band GB=k·u (k default 2) and optional A_USL/A_LSL + O3 mpmath tabulated GB.· View Manifest · CVP overview · Specification
Versions: Calculation 1.0.0 · CVP protocol 1.0.0-proposed · Evidence 2026-09-16.o2-o3
Verification revision: 2026-09-16.o2-o3 · 3/3 property · digest f0b6360d0f41
Legacy regression: 6/6 tests · Production surface contract 4/4
Trust layers: Verification VERIFIED · Production CURRENT · overall VERIFIED
Reference: O1 model · O3 expected_values · O3 numerical_behavior · O2 expected_values · O2 numerical_behavior
Interfaces: PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session. Error-path engine·REST·MCP 1/1 (status, code, calculation_version). SSR compared on URL-canonical requested calculations; empty query is idle (not an error) and JSON-typed object/array inputs are REST/MCP-only.
Supplemental domain review: Not performed
Named expert review: Not performed
CVP suite: 5/5 golden · 3/3 CVP boundary · 6/6 invalid · 3/3 property · 2/2 metamorphic · 8/8 O3 · 4/4 cross-interface · 4/4 CVP contract · Manifest
Sources: JCGM 106:2012 — The role of measurement uncertainty in conformity assessment — 8.2 Guard bands
JCGM 106:2012 — The role of measurement uncertainty in conformity assessment — 7.2 Acceptance interval
Sources
Evidence: 1 legacy golden · 3 legacy boundary · legacy regression suite · 5/5 oracle-backed golden · 6/6 invalid · Artifact integrity PASS
Semantic contract: PASS

Full verification

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

Formulas

Core equations used by this calculator.

Guard bandGB = k · u

Accept USLA_USL = USL − GB

Accept LSLA_LSL = LSL + GB

iSymmetric k·u band on a stated standard uncertainty. Not a process-capability index. Not Monte Carlo. Not ILAC G8 / JCGM 106 risk-based rules.

How to use

Enter standard uncertainty u

u ≥ 0 in the same unit as any specification limits you add.

Set coverage factor k

Defaults to 2. k must be greater than zero.

Optional specification limits

USL and LSL are optional. When present, the page also reports acceptance limits.

Example calculations

Common configurations with formula and result.

k=2 · u=0.5

default coverage

GB=2·0.5

GB=1

With spec

LSL=0 · USL=12 · u=0.5 · k=2

A_USL=12−1; A_LSL=0+1

accept USL=11 · accept LSL=1

Guard Band calculator specification

Version 1.0.0 · Engine tested

Calculation status

Engine tested 6/6 tests · Production surface contract 4/4
Named expert review Not performed
Calculation version 1.0.0

Review policy · Evidence

Definition: GB = k·u. Acceptance USL = USL − GB. Acceptance LSL = LSL + GB. k defaults to 2.
What it calculates: Simple guard band GB=k·u and optional acceptance limits.
Inputs: u
k
usl
lsl
Outputs: GB
accept_usl
accept_lsl
Formula: GB=k·u; A_USL=USL−GB; A_LSL=LSL+GB
Assumptions: GB = k·u with k default 2
Not ILAC G8 / JCGM 106 risk-based decision rules
USL and LSL optional; omitted limits skip that acceptance output
Not Cp/Cpk and not Monte Carlo
Units: same as u / LSL / USL
Boundary conditions: u < 0 → VALUE_OUT_OF_RANGE
k ≤ 0 → VALUE_MUST_BE_POSITIVE
missing u → MISSING_REQUIRED_INPUT
Example: u=0.5 k=2 usl=12 lsl=0 → GB=1 accept_usl=11 accept_lsl=1
Validation cases: 2 published on this page · 6/6 tests · Production surface contract 4/4 · View evidence
u=0.5 k=2 → GB=1
u=0.5 k=2 usl=12 lsl=0 → accept_usl=11 accept_lsl=1
Sources: JCGM 106:2012 — The role of measurement uncertainty in conformity assessment — 8.2 Guard bands
Supports: A guard band is a multiple of standard uncertainty that shrinks the acceptance interval
JCGM 106:2012 — The role of measurement uncertainty in conformity assessment — 7.2 Acceptance interval
Supports: Acceptance limits lie inside the specification interval when a guard band is applied
Calculation version: 1.0.0

Background

Interpretation and common distinctions.

Compute a simple guard band from a stated standard uncertainty.

Supported and not supported

Supported — GB=k·u · optional A_USL and A_LSL · API engineering.process.guard_band

Not supported — ILAC G8 / JCGM 106 risk tables, one-sided risk, Cp/Cpk, Monte Carlo

Agent / API notes

Capability id: engineering.process.guard_band · tool id: guard-band · pin 1.0.0.

{ "u": 0.5, "k": 2, "lsl": 0, "usl": 12 }

Errors: MISSING_REQUIRED_INPUT, INVALID_NUMBER, VALUE_MUST_BE_POSITIVE, VALUE_OUT_OF_RANGE.

Calculator URL stays /calc/engineering/guard-band. There is no /calc/metrology.

Other calculators in this family: Process capability (Cp/Cpk), Test uncertainty ratio TUR, Conformity decision, Type A uncertainty, Type B uncertainty, Gauge R&R, Uncertainty propagate, Tolerance / Uncertainty Workspace, Monte Carlo tolerance .

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Frequently asked questions

Key distinctions behind the calculation.

Is this an ILAC G8 decision rule?