Terms of Service
Last updated: July 1, 2026
Welcome to MonteSheet
These terms govern your use of MonteSheet — the Monte Carlo simulation add-on for Google Sheets. By installing or using MonteSheet, you're agreeing to these terms.
About us: MonteSheet is a product of Pipewriter OÜ, a company registered in Estonia (Sepapaja 6, Tallinn 15551, reg. no. 14904870). We build high-precision computational tools for people who take quantitative risk seriously and would rather not pay $2,900 for the privilege.
MonteSheet Is Not Financial Advice
Let's get this out of the way first, because it matters.
MonteSheet is a highly accurate mathematical simulation engine. It will faithfully execute 100,000 iterations of your formula using the exact distributions you specify, return statistically rigorous P10/P50/P90 outputs, and produce a Spearman-ranked tornado chart of your input sensitivities. It will do all of this beautifully, locally, and fast.
What it will not do is tell you whether your startup will survive, whether the real estate deal is worth it, or whether your project will ship on time. Those answers depend on inputs you provide and judgment you apply. MonteSheet is a simulation tool, not a financial advisor, not an oracle, and not a replacement for human decision-making.
You are solely responsible for your business, investment, and financial decisions. We are not liable for losses, missed forecasts, bad bets, or any other outcomes resulting from your use of the tool — even if the math was perfect.
What MonteSheet Provides
MonteSheet is a Google Sheets add-on that runs Monte Carlo simulations inside your browser. You select an output cell (revenue, cost, NPV — anything your formula computes), assign probability distributions to your input cells, configure iteration count and correlation structure, and run the simulation. Results — histogram, CDF curve, sensitivity analysis, summary statistics — are rendered in the sidebar and optionally written back to your sheet.
The simulation engine runs entirely locally. Your financial model never leaves your computer or passes through our servers. There is no cloud queue, no API call for computation, and no third party that can see your spreadsheet data.
Account Requirements and Access
To use MonteSheet, you need a Google account. You must be at least 13 years old to use MonteSheet. If you are located in the European Union, you must be at least 16 years old, or have parental consent. Authentication for the Pro plan uses license key validation via Gumroad — you purchase once, receive a key, enter it in the sidebar, and it persists via Google's PropertiesService. No ongoing login required.
You're responsible for keeping your license key secure. Don't share it; each key is issued per-purchaser. If you believe your key has been compromised, contact us and we'll sort it out.
Free and Pro Plans
Free
The free tier lets you run simulations with up to 3 input variables, 1,000 iterations, and the three core distributions (Normal, Triangular, Uniform). You get the full histogram and summary statistics. It's a real tool, not a demo.
Pro — $99 lifetime, one-time payment
Pro unlocks the full engine:
- Unlimited input variables
- Up to 100,000 iterations
- All distributions: Log-Normal, PERT, Beta, Poisson, Bernoulli, Discrete Uniform
- Sensitivity analysis via Spearman Rank Correlation (tornado charts)
- Seeded RNG (Mulberry32) for reproducible, audit-ready results
- Raw data export: full simulation matrix written to a new sheet tab
- Chart export and PDF report generation
- Batch scenarios
"Lifetime" means lifetime of the product. If we ever sunset MonteSheet, we'll give you at least 90 days notice and a refund option.
Refunds
If MonteSheet doesn't work for your use case within 14 days of purchase, email us and we'll refund you. No interrogation, no forms. After 14 days, refunds are at our discretion but we're generally reasonable people.
Acceptable Use
You may use MonteSheet for any lawful purpose, including commercial client work. Building financial models for clients and charging them well for it is exactly the use case we built this for.
You may not attempt to reverse engineer the add-on, redistribute it, resell license keys, or use it to produce outputs you then misrepresent as independent third-party analysis. The math is only as honest as the inputs you give it — using MonteSheet to manufacture plausible-looking numbers for misleading purposes is your legal and ethical problem, not ours.
Intellectual Property
The MonteSheet add-on, its simulation engine, and branding are our intellectual property. The underlying @veenie/risk npm package is open-source under MIT and available separately — you're welcome to use it in your own projects without restriction.
Any content you create using MonteSheet — your spreadsheet models, your configured scenarios, your exported reports — belongs to you. We make no claim over your work product.
Google Integration
MonteSheet integrates with Google Sheets through official Google APIs. Your use of MonteSheet is also subject to Google's Workspace Terms of Service. We use Gumroad for payment processing and license verification, so Gumroad's terms also apply to purchases and licensing. We can't override these third parties' policies, but we can tell you that we request the minimum possible permission scopes — see our Privacy Policy for the full breakdown.
Service Availability
MonteSheet's simulation engine runs locally in your browser, which means it works even when our servers don't. The only external dependency for the free tier is the add-on loading from Google's infrastructure. Pro features additionally require a one-time license validation call.
We may update the add-on to add features, fix bugs, or maintain Google API compatibility. Updates are pushed through Google Workspace Marketplace and don't require action on your part.
Limitations of Liability
MonteSheet is provided "as is." We work hard to keep the math right and the software stable, but we can't guarantee it will be error-free or meet every specific need. To the maximum extent permitted by law, our total liability to you is limited to the amount you paid us. We are not liable for indirect damages, lost profits, or business losses.
Changes to These Terms
We may update these terms as the product evolves. We'll post the updated version at montesheet.com/terms-of-service and, for material changes, send an email to Pro license holders. Continued use after changes go live constitutes acceptance.
Governing Law
These terms are governed by Estonian law and EU regulations. For disputes that can't be resolved through friendly conversation, Estonian courts have jurisdiction. For anything under €5,000, we're open to online dispute resolution — it's faster and cheaper for everyone.
Contact
Questions, issues, license problems, or just want to tell us about a gnarly risk model you built:
Email: ivan@montesheet.com
Address: Pipewriter OÜ, Sepapaja 6, Tallinn 15551, Estonia
We respond within 24 hours on business days. For license issues, include your Gumroad order number.
