About this site
One calculator, three articles, and a fairly stubborn commitment to not overstating the answer.
Why it exists
Most people's introduction to Bitcoin is a chart with an arrow on it, or someone shouting a number. Neither tells you anything you can act on, because neither resembles what you would actually have done. You would not have put a lump sum in on the perfect day. You would have put a bit in every payday, for years, through some stretches where it looked like a terrible idea.
That is the question this site answers: what if you had bought a little, regularly, starting then? It uses real daily closing prices, applies exchange rates on the day of each purchase rather than at the end, and shows the result as a money-weighted annual return so that money added last month is not credited with eight years of growth.
The second reason is the one underneath it. A lot of people can feel that their money is going further backwards each year but have never had it explained without either jargon or an agenda. The articles here are an attempt at that explanation, and they are written for someone starting from nothing.
What it will not do
It will not tell you to buy anything. It will not pretend past returns are a forecast, and the falls are stated in the same size type as the gains — Bitcoin has dropped more than 70% from its high on several separate occasions, and the site says so on the front page rather than in a footnote.
It also will not quietly flatter the numbers. The return figure is money-weighted rather than the more generous start-to-finish growth rate. The price history begins on 18 August 2011 rather than reaching back to 2010, because the only data for the earlier period comes from an exchange that traded thinly, kept disputed records and later collapsed — including it would produce bigger headline numbers and worse information.
How it is built
It is a static site: plain HTML generated once a day, with no tracking, no accounts and no server-side processing. The calculator runs entirely in your browser, so the numbers you enter stay on your device. Every result is also computed at build time, which means the page shows a complete, correct answer even with JavaScript switched off.
Bitcoin prices come from Bitstamp's daily closes, one of the longest continuously running exchanges; exchange rates for the non-US currencies come from a separate daily feed and are applied on each purchase date.
Who runs it
One person: Scott Barr, an Australian software engineer who builds small, single-purpose tools that answer one question well. This site is one of a handful; another is bitcoinbythenumbers.com.
It is paid for by advertising, which is why there is an ad on the page and why the privacy page spells out exactly what that means for you. There is nothing to buy here, no newsletter, no affiliate link to an exchange and no referral fee.
Getting in touch
Corrections are genuinely welcome, and are the fastest way to improve the site. If a figure looks wrong, or an explanation does not land, say so: hello@btcdcacalculator.com, or use the contact page.