OC
OneStopCalculators

Author

Avinash Ranjan

Founder & Lead Engineer, OneStop Calculators

I am a software engineer and have been building production software since January 2013 — more than thirteen years across consumer mobile apps, payments and fintech integrations, and data-heavy dashboards. I have led engineering teams at GlobalLogic, 3Pillar Global and Mindmap, and currently work as a lead engineer and consultant through Apps Celestial, shipping apps that serve 150,000+ monthly users. I am also the founder of InterviewGPT, a voice-interview practice product.

OneStop Calculators started as a personal tool. I kept needing the same answers — take-home pay, stamp duty, EMI, the BMI range — and kept finding sites that hid the formula, guessed at the rates, or buried the result under sign-up walls. So I built calculators the way an engineer would: implement the published formula, test it against worked examples, show the working, and keep the inputs on your device.

How the calculators and articles are made

Built from primary sources

Every tax band, threshold and rate comes from the official publisher, and each calculator page states the formula it uses so you can check the maths yourself.

  • United Kingdom: HM Revenue & Customs (HMRC) and GOV.UK rate tables
  • United States: IRS publications and state revenue departments
  • Canada: Canada Revenue Agency (CRA) and CMHC
  • Australia: Australian Taxation Office (ATO) and state revenue offices
  • India: Income Tax Department, RBI and the GST Council

Verified, dated, and corrected

Each calculator is checked against known test cases (for example, HMRC's own worked SDLT examples) before it ships, and again whenever rates change at a Budget or new tax year. Articles carry a published and updated date; the worked examples in them are produced with the calculators themselves.

I use AI writing tools to help draft and structure articles. Every figure, formula and claim is then verified by me against the sources above before publication, and I am responsible for what appears on the site.

What I am not

I am not a licensed financial adviser, accountant, tax agent or doctor, and nothing on this site is personal advice. The calculators give accurate estimates from published rules, but your circumstances may include things a general tool cannot see. For decisions that matter — a mortgage, a tax return, a medical concern — please use the numbers here as a starting point and confirm them with a qualified professional.

Contact and profiles

Articles by Avinash Ranjan