Free tool · Six Sigma

Sigma & Control Chart

Turn defects into a sigma level, combine on time, undamaged and complete into one perfect delivery number, and see on a control chart whether a bad day is a signal or just noise.

1 · Calculator

How good is the process?

Type the numbers from any period. Everything updates as you type, and nothing leaves your browser.

What a sigma level means

Sigma level	Defects per million	Yield	Failures per 1,000

Short-term sigma with the usual 1.5 shift. Most warehouse and delivery processes run between 3 and 4.5 sigma; every step up means roughly three to ten times fewer failures.

2 · Control chart

What you are counting

Defect

Out of

Limits from the first days, optional

Paste from Excel or CSV

One row per day, columns in this order: date, handled, defects, note. Tabs, semicolons or commas all work, and a header row is skipped. A date that is already in the chart is replaced.

Days

No days yet. Add them above, paste from Excel, or .

How to read it

The centre line is your average defect rate. The limits show how far a day can move by normal noise alone, given how much was handled that day.

Outside the limits. One day above the upper limit (or below the lower one). Something was different that day: find it while people still remember.
Shift. Eight days or more in a row on the same side of the centre line. The process has moved: after a change you made, that is proof it worked; without one, find what changed.
Trend. Six days or more in a row, each higher (or each lower) than the one before. Something is drifting: wear, backlog, staffing or a slow change in volume.

Everything else is noise. Asking "what went wrong yesterday?" about a day inside the limits sends people looking for a cause that is not there.

When a signal is worse, take that day through 5 Whys. For daily numbers, use the rows from Damage Control or Incomplete Control per day.

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