Methodology

Live spot prices: CoinGecko (polled every 30 seconds, cached for resilience). Historical daily closes: CoinGecko since 2013; Bitcoinity for 2010–2012. On-chain metrics: mempool.space. Macro / CPI series: FRED. Tax references: IRS, HMRC, Income-tax Act of India, German EStG.

The "DCA since 2013 returns ~57% CAGR" figure on the DCA calculator and About page is computed as:

btc_acquired_t = Σ (contribution_i / close_i)
portfolio_t    = btc_acquired_t × spot_t
CAGR           = (portfolio_t / total_contributed) ^ (1 / years) − 1

Window: 1 Jan 2013 → most recent UTC close. Daily contribution at 09:00 UTC, no fees. Past performance ≠ future performance.

Future BTC price uses a configurable CAGR (default 18% — the 2017–2024 trailing 7-year median) compounded annually. Withdrawals use the safe-withdrawal model: spend_t = portfolio_t × swrwith swr defaulting to 4%. Inflation discount uses long-run US CPI of 2.5%.

Implements Giovanni Santostasi's regression: log10(price) = a · log10(days_since_genesis) + b with a ≈ 5.82, b ≈ −17.01. Coefficients re-fit monthly against all daily closes since 3 Jan 2009.

US federal brackets and capital-gains rates are the 2025 IRS schedule. UK CGT uses the 2025/26 HMRC rates (£3,000 allowance, 18% / 24%). India follows §115BBH (30% + 4% cess + 1% TDS). Germany follows §23 EStG (12-month exemption, €1,000 Freigrenze). Estimates only — confirm with a qualified professional before filing.

• No exchange-fee or slippage model on historical backtests.
• USD-only base currency for return calculations; fiat conversion is display-only.
• On-chain metrics depend on mempool.space availability.