Control charts and Cpk without the $2,000‑a‑year license.
Paste your measurements, or snap a photo of the check sheet, and get control limits, rule violations and Cpk in seconds, each with a plain-English verdict. Nothing to install, and your data never leaves your browser.
- Matches NIST worked examples
- 30-day refund, any reason
- Mac, Windows, any browser
Paste, chart, read the verdict
1. Paste or scan your data
Paste a column from Excel or Sheets, drop a CSV, or scan a photo, PDF, Word or Excel sheet.
2. See the chart
Control limits, spec limits and the Nelson rules you choose (all 8 available, 5 on by default) are checked instantly. Signals are marked on the chart.
3. Read the verdict
Cp, Cpk, Pp and Ppk with a plain-English verdict and the next step to take.
Checked against NIST's published examples
Every release runs an automated test suite that compares results to the worked examples in the NIST/SEMATECH e-Handbook of Statistical Methods. A release that fails a check doesn't ship.
Every number on the validation page is recomputed from the deployed code each time the site is published, with the published source, expected value, LimitLine's value and tolerance. Download the datasets and rerun them in LimitLine, Minitab or Excel yourself.
Free forever, or Pro for one payment
Free
- Charts I-MR with all 8 Nelson rules, Cp/Cpk/Pp/Ppk with histogram, Pareto and run charts, the "which chart?" guide
- Scan 1 photo, PDF, Word or Excel scan a day
- Help step-by-step guide, examples and a help assistant on every screen
- Customize your titles, units, target line and Cpk goal; color-blind-safe and print styles
- Save your work project files with your data and settings, kept on your device
Pro, founding license
Everything in Free, plus:
- Scan a photo, PDF, Word or Excel sheet, or a chart, into numbers; 20 a day
- More charts X̄-R, X̄-S, p, np, c, u, EWMA, CUSUM, Laney P′/U′ and G
- Analysis t-tests, ANOVA, proportions, chi-square, regression, gauge R&R, 2-level DOE, non-normal capability
- Lean and Toyota tools OEE, takt and line balance, kanban, heijunka, standard work, A3, Toyota Kata
- Customize limits from a baseline, excluded points, point notes, dates or lots, ±1σ/2σ zones
- Export one-page PDF report; PNG, SVG and CSV
- Updates every 1.x update included, no renewal fee
Secure checkout hosted by Stripe. Your card details never touch this site.
Student
- What you get every Pro feature in the app, 20 scans a day and every 1.x update included
- Who qualifies students at a college, university or training school with a school email address, and Green or Black Belt candidates enrolled in a course or registered for an exam (we check by email)
- How it's checked confirm your school email with a 6-digit code, then pay. One Student license per person.
Pro unlocks the moment you pay: your license key arrives on the confirmation page and by email, with a link that unlocks it on any device. Refunds within 30 days for any reason.
All prices in US dollars (USD). Payments are processed securely by Stripe; sales tax, where it applies, is added at checkout.
Teams: saved history, live data links, alerts and scheduled PDF reports are planned as monthly Team and Expert plans. They aren't on sale yet. Email me when Team plans open
Published prices, side by side
| Product | Price | How you pay | Runs in |
|---|---|---|---|
| LimitLine Pro | $29 | One-time (founding price, then $49); free plan available | Any modern browser; calculations stay on your device |
| MetricGate | $0–$99/mo | Free tier (10 runs a month), paid plans monthly (metricgate.com) | Browser; analysis runs on their servers |
| numiqo (formerly DATAtab) | €69.50/yr | Per year, single user; shorter and company plans too (numiqo.com) | Browser |
| SPC for Excel | $329 | One-time, per user (spcforexcel.com) | Microsoft Excel add-in |
| QI Macros | $379 | One-time, single user (qimacros.com) | Microsoft Excel add-in |
| SigmaXL | $399 | One-time, single user, first year of support included (sigmaxl.com) | Microsoft Excel add-in |
| EngineRoom (MoreSteam) | $495/yr | Per year, individual license (moresteam.com) | Browser |
| JMP | $1,390/yr | Per year, single user (store.jmp.com) | Windows and macOS |
| Minitab Statistical Software | $1,995/yr | Per year, single named user (minitab.com) | Desktop and web |
Prices in US dollars unless marked, as published on each vendor's own pricing page, checked October 21, 2026; they may have changed since. These products include features LimitLine doesn't, so compare the tools you actually need. Product names are trademarks of their owners; LimitLine isn't affiliated with any of them.
Built from 109 real complaints about today's SPC tools
Reviews and forum threads about Minitab, JMP, SigmaXL, QI Macros, SPC for Excel and EngineRoom, sorted complaint by complaint. Two-thirds fall into four problems:
| What users complain about | Share | What LimitLine does |
|---|---|---|
| Price and licensing | 27.5% | Core charts and Cpk are free forever. Pro costs a fraction of a desktop license, with a student price. |
| Knowing which chart to use and what the result means | 19.3% | A "which chart do I need?" guide asks two or three questions and opens the right chart. Every analysis ends with a plain-English verdict. |
| Getting data in | 10.1% | Paste straight from Excel or Sheets, or drop a CSV file on the box. Header rows are skipped automatically. |
| Being tied to an Excel add-in | 9.2% | Runs in any modern browser. Nothing to install, nothing for IT to approve. |
How we counted: in October 2026 we read public reviews on Capterra, G2 and TrustRadius and threads on quality forums (Elsmar Cove, Zeiss), and coded each distinct complaint into one category; 109 complaints in total. Review sites lean positive and some reviews are vendor-solicited, so treat the shares as a rough guide, not a survey.
Everything here already works
Built, tested, and dated
- BuiltI-MR charts, 8 Nelson rules, Cp/Cpk/Pp/Ppk, histogram
- BuiltX̄-R and X̄-S subgroup charts (n = 2–25)
- Builtp, np, c and u attribute charts with variable sample sizes
- Built"Which chart?" guide, CSV drop, copy chart image
- BuiltAnalysis tools: Pareto, run chart, Capability+ (non-normal), hypothesis tests, regression, gauge R&R, 2-level DOE, EWMA, CUSUM, Laney P′/U′, G chart, each checked against NIST, scipy or statsmodels
- BuiltScan from files: PDF (text and scanned pages), Word tables, Excel sheets, CSV
- BuiltLean and Toyota tools: OEE, takt and line balance, kanban, heijunka, standard work, A3 report, Toyota Kata
- BuiltScan from image: number sheets (on-device reader) and graphs (click the scale, points found by color)
- LivePro and Student licenses on sale; Pro unlocks the moment you pay
- BuiltOne-page PDF report, save and open project files, phone layout with the chart on the first screens
- BuiltPublic validation page: 341 reference checks with sources and downloadable datasets
- PlannedTeam and Expert monthly plans: saved history, live data links, alerts, scheduled reports, automatic analysis reports
Before you buy
Can it read a photo of my check sheet?
Yes. Free includes 1 scan a day so you can try it; Pro and Student include 20 a day; Team and Expert scan without a daily limit. Printed, typed and screenshot tables read best. Messy handwriting is less reliable, so every number appears in an editable table before it is used, and doubtful cells are highlighted. For graphs, you click two gridlines and one data point and LimitLine finds the rest; in testing it recovered all 20 points of a chart to within 0.04 units. PDF, Word (.docx), Excel (.xlsx) and CSV files work too: typed files are read exactly from the file, with no guessing, and one file counts as one scan (CSV is free, like pasting). The reading happens on your device; nothing is uploaded.
Is my data uploaded anywhere?
On Free and Pro, no. All calculations run in your browser and nothing is sent to a server. On Team and Expert, only the projects you choose to save are stored, so they can sync and send reports. Privacy policy
Does it work on a Mac or a locked-down work laptop?
Yes, anything with a modern browser. There is nothing to install.
How do I know the numbers are right?
Every release is tested against published worked examples (NIST, AIAG, Montgomery and others); the validation page lists every check with its source and the datasets so you can rerun them, and the formulas are shown in the app. Capability results assume a stable, roughly normal process, and the tool tells you when special-cause signals make capability unreliable.
Is this a replacement for Minitab?
For control charts, capability, and the everyday Six Sigma and lean tools (hypothesis tests, regression, gauge R&R, 2-level DOE, OEE), it aims to be. It isn't a full statistics package: there's no reliability analysis, response surfaces or Tukey comparisons yet, and it won't pretend otherwise.
Can my company use it for compliance?
LimitLine calculates statistics; it doesn't certify a process or replace a qualified engineer's judgment. Validate it against your own procedures before relying on it for regulated work.
Who can buy the Student license?
Anyone enrolled at a college, university or training school who can receive email at a school address, and Green or Black Belt candidates enrolled in a course or registered for a certification exam. Click “Get Student”, confirm your school email with a 6-digit code, then pay. No school email, or a school we don't recognise? Email [email protected] with proof of enrollment (a class schedule, enrollment letter or exam registration, with ID numbers, photos and dates of birth covered) and we'll send you a Student link, usually within 2 business days. We delete the proof after checking. One Student license per person.
What does “every 1.x update included” mean?
Your one-time license gets every LimitLine 1.x release (new charts, tools and fixes) at no extra cost and keeps working for good. If there's ever a version 2 with a separate price, your version 1 license keeps working.
Can my company pay by invoice or purchase order?
Not yet. Checkout takes cards, Apple Pay, Google Pay and other methods through Stripe, and the receipt shows the tax, so most people expense it. Need an invoice for a larger order? Email us.
Do I need a subscription?
No. Free stays free and Pro is one payment. Monthly plans are for teams that want saved history, alerts and automatic analysis reports.
I lost my key, or I want Pro on another device
Your key is emailed to you when you pay, with a link that unlocks LimitLine on any device: phone, work computer or a new browser. Can't find the email? In the app, open License, choose “Lost your key, or using a new device?” and enter the email you paid with; we send it again, only to that address. One license covers you on all your own devices.
What if I want a refund?
Email [email protected] within 30 days of a payment, for any reason, and we'll refund it in full; the license key for that purchase then stops working. See the refund policy.
Lock in the founding price
$29 one-time for the first 200 buyers, then $49. Pro unlocks the moment you pay; refunds within 30 days for any reason.