Pay once. There is nothing to cancel.

All 18 tools open with no account. 11 are free end to end, and the other 7 run live on their sample data so you can see exactly what you would be buying before you buy it. A licence buys one thing: the right to put your own measurements in.

No auto-renewal, and no way to add one. Every purchase here is a one-time payment. No card is kept on file, there is no subscription to cancel and no account to close — we could not rebill you if we wanted to. When a term ends, the tool goes back to running on its sample data and nothing else changes.

Free

Available now

$0forever

Every tool opens and runs. No account, no upload.

11 of the 18 tools, free end to end
The other 7 open and run live on their sample data — a licence lets you swap in your own
Up to 5,000 rows per chart
SVG and PNG export at 2× and 4×, with the estimator, constants and rule set drawn into the figure
Nothing is uploaded and there is no account
Exports carry a small “made with spcplot.com” credit

Start charting

Single tool

$20one time, 30 days

One study to finish, one tool to finish it with.

Which tool?

Chosen before checkout, and written into the licence key itself.

One Pro tool of your choosing, with your own data
30 days from the moment you buy it
One payment. Nothing is stored to charge again
The 11 free tools, as always
Exports still carry the credit line

Pro

$149one time, 12 months

The whole set, for the people who sign the report.

All 7 Pro tools, with your own data
12 months from the date of purchase
Clean exports — no credit line
Up to 100,000 rows per chart
Any Pro tool added during the 12 months, included

Lifetime

Founding licence

$249one time, forever

Founding licence — the first 200 only.

Everything in Pro, permanently
One payment, no renewal, no expiry date
Every tool added later, included
Limited to the first 200 licences

Validated against published worked examples → — the source, the data, the method and the automated test, for every number this site reproduces.

All purchases are final. Every tool runs in full before you pay — the 7 Pro ones included, live on their sample data — so there is nothing about a licence you cannot see first. Key not working? help@spcplot.com. Full terms.

Checkout is not open yet. Every tool on SPCPlot is fully usable in the meantime — the 11 free ones with your own data, and the 7 Pro ones on their sample datasets.

Questions people actually ask

Is this a subscription?: No, and it cannot become one. Each of the three licences is a single payment. Stripe takes the money in one-time mode, which stores no payment method, so there is nothing on file that could be charged again — no card, no mandate, no account. When a licence runs out it simply stops applying; nothing is deducted and nothing is cancelled.
What is actually locked?: Only one thing: entering your own measurements into one of the 7 Pro tools. Those pages are not hidden and not crippled. The route loads, the engine loads, the sample dataset renders as a live chart, every option redraws it, and you can export the figure. What a licence buys is the right to replace the demonstration data with yours. The other 11 tools are free end to end and always will be.
What does the $20 single-tool licence cover?: One Pro tool, which you pick before checkout, for 30 days. The tool's id is written into the licence key itself, so the key unlocks that page and no other. It is there for the common case: one capability study or one gauge assessment to finish this month, with no interest in the rest of the suite. It does not remove the export credit line — Pro and Lifetime do.
Seven single tools would cost less than Pro. Why buy Pro?: Because they are not the same thing. A single tool runs 30 days; Pro runs twelve months, covers every Pro tool including ones added during the year, raises the row ceiling, and removes the credit line from exported files. If one study is all you need, the single tool is genuinely the right purchase and it is priced so that it is.
What happens when I pay — do I get an account?: No. You get a licence key: one line of text, signed by us, that your browser checks on its own with no network call. It is shown on the page you land on after paying and applied to that browser immediately, and the same page offers it as a text file to keep. There is no password to forget, nothing to log into and no customer record on our side — Stripe holds the payment record, we hold nothing.
Where do I keep the key, and what if I lose it?: Two places, in the order worth trying. First, the licence file: the activation page offers a “Download licence file” button, and that .txt holds the key, what it covers, when it expires and the restore procedure, with no internet connection needed. A password manager does the same job. Second, your browser history: the activation address you landed on after paying re-issues the same key with the same expiry, as many times as you need. We keep no copy of your key, so those are the routes there are — and it is worth saving it in the two minutes after you buy rather than the six weeks after.
Can I use the figures in a report, a PPAP submission or a paper?: Yes, on every tier, including the free one. The figures are yours. The “made with spcplot.com” credit on a free export is a credit, not a licence restriction. What you may not do is treat any of it as a disposition authority — see the terms.
How many machines can I use one licence on?: As many as you like. A key is a bearer token: it lives in the browser you pasted it into, and pasting it into another browser works. There is no seat count and no activation limit, because enforcing one would need an account and a server, which would cost the privacy property that is the reason to use this site at all.
Can I have a refund?: No — all purchases are final, and it is worth saying why that is fair rather than leaving it in the fine print. Every one of the 18 tools runs in full before you pay: 11 are free end to end, and the 7 Pro ones load the real engine, draw the real figure from their sample dataset and export it. Nothing about the paid product is hidden from someone who has not paid, so a few minutes on the site answers the question a refund would otherwise have to. What is not covered by that is a licence that does not work: if your key will not activate, write to help@spcplot.com and it will be fixed, and a duplicate charge goes straight back. 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.
Is my data uploaded when I pay?: No. The payment endpoints handle a product name and a Stripe session id and never see a measurement — there is no code path that could send one. Card details are entered on Stripe’s own hosted page and never touch this site. Everything you paste into a tool stays in the browser tab, on every tier.