Most property calculators are broken by design.

They ignore local tax law. They use round numbers that don't reflect reality. They stop at gross yield without telling you what actually lands in your pocket. And the good ones — the ones built by accountants or mortgage brokers — are buried behind consultations or subscription fees.

MMDAI was built to fix that. Real formulas. Real tax logic. Real local context. Free, in the browser, without asking for your email address.

Calculators built for personal use first.

The person behind MMDAI has spent over 15 years working across project management, operations, and investment — building systems, running businesses, and making the kind of financial decisions that require tools that actually work.

When evaluating property investments across different European markets, the available tools kept falling short. SDLT with the BTL surcharge. Section 24 vs limited company. Grunderwerbsteuer across 16 Bundesländer. LMNP réel vs micro-BIC. No single tool handled any of these correctly — let alone all of them.

So they were built from scratch. Then made public. Then expanded to cover more markets, more edge cases, more of the real complexity that investors actually face.

Maintained, updated, and honest about limitations.

Tax law changes. SDLT thresholds shift. Bundesland rates get updated. LF 2025 rewrote the LMNP exit calculation overnight. Every calculator on this site is reviewed and updated when the underlying rules change — not left to go stale.

Every calculator includes a disclaimer because these are tools for informed decision-making, not substitutes for professional advice. The goal is to help you arrive at the conversation with your accountant or broker already knowing the right questions to ask.