Terms

What this is

SPCPlot is a set of calculation and visualisation tools that run entirely inside your web browser. There is no account, nothing to install, and none of the data you chart is sent to a server.

Most of the tools are free end to end. The professional ones open, run their sample dataset live and export it for free as well; a licence buys the right to enter your own measurements into them.

Every licence is a one-time payment — not a subscription, with no renewal and no stored payment method. Checkout is not yet switched on, so nothing can be bought at the moment; the pricing page lists what each licence will cover and what it will cost.

A licence key is a bearer token: whoever holds the string may use it, on as many browsers and machines as they like. There is no seat count, no activation limit and no revocation, and we keep no copy of any key that has been issued.

It is a calculation aid, not an authority

SPCPlot computes control limits, capability indices, measurement-system statistics and sampling plans from the data you provide. It does not decide whether a process is capable, whether a gauge is acceptable, or whether a lot should ship. Those are engineering judgements made by a qualified person inside a quality system.

Manufacturing SPC frequently sits inside regulated quality systems — FDA 21 CFR Part 820 and Part 11, AS9100, IATF 16949. A browser tool with no accounts, no audit trail and no electronic signatures cannot be a compliant record system, and this one does not claim to be. Validating any tool for use in your quality system is your responsibility under that system.

What is claimed about accuracy, and what is not

The /validation page lists every published worked example this site reproduces, with the source, the data, the method and the automated test that asserts it. Those claims are specific and checkable, and they are the only accuracy claims made.

SPCPlot is not certified, approved or endorsed by AIAG, ISO, ASTM, ANSI, ASQ, NIST or any standards body, and no conformance to any standard is claimed. Where a method comes from a published source, that source is named. Where a source is paywalled, only facts — numeric thresholds, formulas — are used, and none of its text is reproduced.

No warranty of any kind is given. To the fullest extent the law allows, the operator of this site is not liable for any loss arising from use of it.

Your data

You keep every right in the data you paste in and the figures you export. The site never receives either, on any tier, licensed or not.

Refunds

All purchases are final. Every tool runs in full before you pay — the professional ones load the real engine, draw the real figure from their sample dataset and export it — so nothing about the paid product is hidden from somebody who has not paid.

That does not cover a licence that does not work. If a key will not activate, write to help@spcplot.com and it will be sorted out, and a duplicate charge is returned. If you are a consumer in the EU or the UK, completing checkout is a request for immediate delivery of digital content and waives the 14-day withdrawal right once the key has been issued; your rights if the product is faulty are untouched.

Getting in touch

Questions, corrections and disagreements about a published number: help@spcplot.com. A reproducible disagreement with a source is the most useful message this site can receive.