About CalcMate

30 free calculators, built and maintained in Taichung, Taiwan.

Who makes this

CalcMate is built and maintained by Digimate (數伴有限公司 (Digimate Co., Ltd.)), a small web design and CRM consultancy based in Taichung, Taiwan. Our day job is building websites and streamlining business processes for clients — which is where these calculators came from.

The site is run by Chen Chien-Yu, who goes by Fish Chen. If something here is wrong, unclear, or missing, it lands in one inbox and one person answers it: hello@calc-mates.com.

Why it exists

These started as internal tools. Client work throws up the same small calculations over and over — working out a percentage change for a report, checking how a loan term affects total cost, converting units for a spec — and we kept rebuilding them or hunting for a page that would answer the question without three popups and a newsletter prompt.

Enough people asked for access that publishing them properly made more sense than sending links to half-finished internal pages. That is the whole origin story. There is no growth plan behind it beyond keeping the tools accurate and adding ones we actually need.

How each calculator is checked

Every tool here runs entirely in your browser, so the arithmetic is visible and verifiable rather than hidden behind an API. Before a calculator ships, it goes through the same three steps:

1. The formula is taken from a published source, not reconstructed from memory. Where a tool relies on established thresholds or an academic equation — the WHO’s BMI bands, the Mifflin-St Jeor equation, ACOG’s dating guidance — the reference is listed at the bottom of that tool’s page so you can check it yourself.
2. Outputs are verified against worked examples computed independently of the site’s own code, so a bug in the implementation cannot quietly validate itself.
3. Edge cases are handled explicitly rather than left to produce nonsense: leap years, real calendar month lengths, zero denominators, overnight shifts that cross midnight, and temperature scales that do not share a zero point.

What we will not do

No accounts, no signup walls, and no interstitials between you and the answer. Nothing you type into a calculator is transmitted, logged, or stored — it never leaves your device, which you can confirm in the privacy policy.

The health and finance tools are informational. They implement well-documented formulas accurately, but a formula is not a diagnosis and not financial advice. For decisions that matter, the number here is a starting point for a conversation with a professional, not a replacement for one.

Corrections

If you find an error, tell us and it gets fixed — accuracy is the only thing this site has going for it. Email hello@calc-mates.com with the tool and the inputs you used, and you will get a reply from a person.