Can this check a negative-only tolerance?

No, this page specifically models nominal to nominal plus an upper allowance. Use the actual lower and upper limits for a negative-only drawing.

Why can nominal itself miss acceptance?

An inward guard band raises the lower acceptance limit above nominal. That follows your chosen decision rule, while nominal remains a valid drawing boundary.

May the nominal be negative?

Yes, signed values are valid for datum-relative dimensions. The allowance and measurement must use that same reference.

Does a zero guard band remove the drawing tolerance?

No, it makes the acceptance limits equal to nominal and nominal plus the allowance. The upper drawing width still applies.

Quality & Metrology calculator

Upper Unilateral Tolerance Calculator

Evaluate a drawing dimension that permits variation only above nominal. Supply the upper allowance, corrected measurement and agreed inward guard band.

What this calculator does

Check a measured dimension against an upper-only tolerance and an entered acceptance guard band.

Formula used

Specification limits = nominal, nominal + upper allowance
Acceptance limits = lower specification + guard band, upper specification − guard band
Acceptance margin = min(measured − lower acceptance, upper acceptance − measured)
Deviation = measured − nominal

Inputs explained

Nominal Dimension: Nominal or datum-relative value from the controlled drawing.
Upper Allowance: Full permitted drawing width before applying the acceptance guard band.
Measured Dimension: Corrected measurement result for the same dimension.
Inward Guard Band: Per-edge allowance from your agreed measurement decision rule.

How to use the result

Best suited to upper allowance Inspection, Datum-Relative position check.
Only positive-direction unilateral allowances are modeled. A guard band does not independently establish a coverage probability.

Current U.S. benchmarks

U.S. manufacturing runs at 75.7% of capacity (Federal Reserve, Aug 2026). New factory orders are up 8.5% year over year (Census).

Common questions

Can this check a negative-only tolerance? No, this page specifically models nominal to nominal plus an upper allowance. Use the actual lower and upper limits for a negative-only drawing.
Why can nominal itself miss acceptance? An inward guard band raises the lower acceptance limit above nominal. That follows your chosen decision rule, while nominal remains a valid drawing boundary.
May the nominal be negative? Yes, signed values are valid for datum-relative dimensions. The allowance and measurement must use that same reference.
Does a zero guard band remove the drawing tolerance? No, it makes the acceptance limits equal to nominal and nominal plus the allowance. The upper drawing width still applies.

Last reviewed 2026-10-06.