Process Capability Analysis

Process Capability Analysis — Cp, Cpk, Pp & Ppk, made simple

Is your process good enough to stay inside spec? Process Capability Analysis turns a handful of measurements into the numbers quality engineers actually use — Cp, Cpk, Pp and Ppk — and draws the classic capability histogram and individuals control chart so you can SEE what the numbers mean. It is fully offline, tiny (~3 MB), and free of clutter.

Whether you are studying Six Sigma, preparing a PPAP, running a line audit, or just learning SPC, this app gives you a fast, honest read on how well your process fits its specification limits.

WHAT YOU GET

• Live capability indices — enter your LSL, target and USL plus your measured values and watch Cp, Cpk, Pp and Ppk update instantly.
• Within and overall sigma — short-term spread from the average moving range (MR / 1.128) for Cp/Cpk, long-term spread for Pp/Ppk, so the gap between them tells you how stable the process really is.
• Expected PPM and process sigma level — defect rate estimated from the normal distribution, plus observed out-of-spec counts.
• Capability histogram — your data as bars with the fitted normal curve, the spec limits and the target line, so off-centre and over-spread processes are obvious at a glance.
• Individuals (I) control chart — points with the +/- 3 sigma control limits to check stability BEFORE you trust a capability number.
• Plain-language verdict — a quick "capable / not capable" read against the common Cpk >= 1.33 bar.

EASY, FLEXIBLE INPUT

• Type any value by hand, OR fine-tune with a slider and the plus / minus buttons — whatever is faster for you.
• Add and remove measurements freely; your spec limits, target and every value are saved automatically, so you never lose your work.

LEARN AS YOU GO

• A friendly Concept tab explains capability with the "doorway" analogy: Cp asks if the doorway is wide enough, Cpk asks if you are also walking down the middle.
• The exact formulas are rendered with KaTeX — clean, properly typeset maths that never overlaps — and they work completely offline.
• A Simulate tab lets you drift the mean off-centre or widen the spread on a fixed spec and watch Cpk fall and PPM climb.
• Ready-made example datasets (capable and centred, off-centre, too much spread, six-sigma) load with a single tap.

BUILT RIGHT

• 100% offline — no network access required and none requested for the maths.
• No accounts, no tracking of your measurements.
• Lightweight, fast, and designed with a clean "Graphite Lime" look.

DEFINITIONS AT A GLANCE

• Cp = (USL - LSL) / 6 sigma — spec width vs spread (ignores centring).
• Cpk = min((USL - mean) / 3 sigma, (mean - LSL) / 3 sigma) — capability including centring.
• Pp / Ppk — the same idea using the overall (long-term) spread.

Note: capability assumes a stable, roughly normal process. Always check the control chart first — if points stray outside the limits, fix that before trusting Cpk.

Download Process Capability Analysis and get a clear, instant answer to the only question that matters: can the process stay inside spec?