About Sumvia

Sumvia is a publication about the arithmetic of running a business. It covers the numbers a founder, freelancer, or shop owner actually handles in a week — what to charge, what a discount costs, where break-even sits, whether a spend returned anything, what a growth rate honestly was, and what the hours on a time card add up to. Each topic gets one focused page: the formula stated plainly, an interactive calculator, worked examples, and the limits of the method spelled out.

Why business math

Business math is where small calculation mistakes cost real money, and where the mistakes are rarely arithmetic slips. They are base errors: markup quoted as margin, total growth divided by years and called an annual rate, a discount stacked on a discount and read as their sum, lifetime value computed from churn data too young to trust. A general-purpose calculator cannot catch any of that, because the keys do not know which base you meant. A page built around one specific question can — by always showing the sibling figure (margin beside markup, compound rate beside naive average) so the confusion is visible before it becomes a price list.

Sumvia began as a broader catalog of everyday calculators. In August 2026 we narrowed the publication to the business cluster, where focused pages genuinely help, and stopped competing to be the hundredth page that computes a percentage. Tools outside the cluster that people had bookmarked remain live and functional; they are simply no longer what Sumvia is about.

Worked examples that cannot drift

Every calculation engine on Sumvia is a small, typed function with automated tests covering standard inputs, decimals, negatives, zeros, and edge cases such as division by zero and overflow. The worked examples in the prose and FAQs are not typed in by a writer — they are computed at build time by the same engine that powers the interactive calculator on that page. If an engine change would make a published example wrong, the site fails to build until the prose and the code agree again. That discipline is the whole reason to trust a calculator site, and it is documented in detail on the methodology and accuracy page.

Browser-native, no accounts

Sumvia tools run entirely in your browser. The values you type are processed on your device and never sent to our servers — there is no registration, no login, and no stored user profile. This is a deliberate design constraint, not a temporary state: a calculator should be usable instantly and leave nothing behind. The site is static; what you download is the whole product.

The studio behind it

Sumvia is the home base of a small independent studio that builds single-purpose web utilities, each on its own domain: fitnesscalculator.net for fitness math, invoicesandreceipts.com for in-browser invoice and receipt PDFs, charlimit.net for character-limit checking, keepsakecodes.net for printable QR keepsakes, and tossthatcoin.com for a fair coin toss. The same engineering standard applies across the network: typed engines, automated tests, no accounts, and pages that state their limits.

Verify consequential results

Sumvia pages are aids for business arithmetic, not professional advice. Margins, break-even points, and return figures computed here use the stated formulas on the numbers you supply; they know nothing about your tax position, your contracts, or your risk. Independently verify any result before relying on it for a consequential financial, legal, tax, or business decision. Where a tool's model has known limitations — the SaaS metrics page's simple LTV model is a good example — the page says so plainly.

Get in touch

Found a problem, or want to suggest a business-math topic? See the contact page — reports of suspected calculation issues are especially welcome and are treated seriously.