Uncertainty Budget is a structured tabular analysis listing all sources of measurement uncertainty, their magnitudes, types, distributions, and contributions to the combined uncertainty — the systematic documentation of every error source in a measurement process, organized to calculate the total uncertainty.

Uncertainty Budget Structure

• Source: Description of each uncertainty contributor (repeatability, calibration, temperature, resolution, etc.).
• Type: A (statistical) or B (other means) — classification per GUM.
• Distribution: Normal, rectangular, triangular, or other — determines divisor for standard uncertainty.
• Standard Uncertainty: Each source converted to a standard uncertainty ($u_i$) in the same units.
• Sensitivity Coefficient: How much the measurement result changes per unit change in each source ($c_i$).

Why It Matters

• Transparency: The budget makes all assumptions explicit — reviewable and auditable.
• Improvement: Identifies the dominant uncertainty contributors — focus improvement on the largest sources.
• ISO 17025: Accredited laboratories must maintain uncertainty budgets for all reported measurements.

Uncertainty Budget is the blueprint of measurement doubt — a comprehensive accounting of every uncertainty source for transparent, traceable, and improvable measurement results.