About DigitSum

Calculators that respect your time and your intelligence.

DigitSum is built to make calculators feel trustworthy again: fast, transparent, verifiable, and useful on the first screen.

Last updated: March 2026

Why DigitSum exists

Too many calculator sites are bloated, opaque, and built like content farms.

Search for a mortgage, tax, BMI, or unit converter and you will usually find pages overloaded with ads, padded with generic filler, and vague about where the numbers come from. That makes simple tools harder to trust than they should be.

DigitSum exists to do the opposite. The goal is to show the calculator quickly, explain the logic clearly, and make it possible to verify what the tool is doing without digging through a maze of distractions.

That matters most in categories where people are making real decisions: finance, tax, income, health, and other practical calculations where assumptions, rounding, and source quality can materially change the result.

Founder

Built by Jan Křenek in Prague

Jan Křenek Founder and software developer · Prague, Czechia

Personal website LinkedIn

Hi, I'm Jan Křenek, a software developer based in Prague. I build DigitSum as an independent calculator library for people who want fast tools, visible formulas, and enough context to understand the answer. I am not presenting the site as professional financial, tax, legal, or medical advice; the practical expertise here is in implementing formulas carefully, testing outputs against references, and documenting assumptions clearly.

✓ Independent builder focused on clarity, speed, and transparent formulas.
✓ Registered self-employed entrepreneur in the Czech Republic.
✓ Treating methodology, assumptions, correction reports, and source context as part of the product, not as an afterthought.

Operator and legal identity

A real, verifiable publisher

DigitSum is operated by Jan Křenek as a self-employed entrepreneur registered in the Czech Republic. Registration details are listed in the legal notice.

Operator: Jan Křenek
Country: Czech Republic

Verify in ARES

How it's built

Built for trust, not engagement

Private by default

DigitSum calculators are designed so the actual calculations happen in the browser. The goal is to let people test sensitive numbers without turning every input into a data collection event.

Local-first calculator behavior

Formula-first, not copy-first

The formula, assumptions, rounding behavior, and worked examples matter as much as the interface. Copy is there to explain the math, not to bury it under SEO filler.

Methodology on every calculator page

Designed for multilingual use

Locale support is part of the architecture, not a wrapper added later. Routes, formatting, currencies, units, and UI copy are structured so the same calculator can work cleanly across 50 supported locales.

50 supported locales

The story so far

From frustration project to a broader calculator library

Early build

The first calculators solved personal frustration

DigitSum started from a simple problem: too many calculator pages were slow, padded, and hard to trust. The first tools were built to be faster, clearer, and easier to verify.

Architecture

Formula logic and content were separated early

Calculation logic moved into dedicated modules, while explanations, assumptions, and FAQs were structured separately so the same math could power multiple interfaces cleanly.

Localization

Multilingual support became a product feature

Instead of treating translation as cosmetic, DigitSum started organizing routes, units, formatting, and content so calculators could feel native across 50 supported locales.

Today

The site is growing into a broader reference library

The goal now is not just to publish more calculators, but to keep raising the trust standard around methodology, clarity, speed, and source transparency.

What DigitSum commits to

Show the tool before the filler

The calculator should be visible quickly so users can get value immediately. Explanations matter, but they should support the tool rather than bury it.

Explain the formula and assumptions

If a result depends on a formula, default, category threshold, or rounding rule, that context should be visible in plain language so the output is understandable rather than mysterious.

Verify the math against references

Calculator logic is checked against known examples, reference implementations, and source material so the numbers are not just plausible, but reviewable.

Keep the tools free and low-friction

No account should be required to use core calculators, and no basic result should be pushed behind a paywall. The tool should feel useful immediately.

Build for international use from the start

Copy, formatting, currencies, units, and routes are structured so DigitSum can expand cleanly across 50 supported locales instead of treating non-English support as an afterthought.

124 Free calculators

50 Languages supported

0 Required accounts

0 Paywalled features

Start with the tool, then inspect the math.

Browse the calculators if you already know what you need, or read the methodology if you want to see how DigitSum approaches sources, assumptions, and ongoing review.

Questions, corrections, or partnerships? Write to hello@digitsum.com.

Browse all calculators Read methodology