Bitcoin monthly investment calculator

A monthly contribution, not a one-time investment

The amount entered is contributed again every month. There is one purchase in the selected month and another in every subsequent available month, always at the day-1 open at 00:00 UTC. The USDT amount is fixed, not the BTC quantity: each purchase obtains a different quantity depending on its price.

The final month is included when its purchase is available before the valuation cutoff. There are no daily purchases or current-month prorations. Dates use UTC, regardless of the user's local time zone.

How the result is calculated

A is the monthly contribution, Pᵢ is each purchase's opening price, N is the purchase count and P final is the latest available daily close. Calculation takes place on the server:

• BTC from each purchase = A / Pᵢ.
• Accumulated BTC = the sum of the quantities from all purchases.
• Total contributed = A × N.
• Final value = accumulated BTC × P final.
• Profit or loss = final value − total contributed.
• Percentage result = (profit or loss / total contributed) × 100.
• Average cost per BTC = total contributed / accumulated BTC.

The percentage is not an annualized return or a rate adjusted for the timing of each contribution. The result is unrealized because the simulation does not sell BTC. Results are rounded for display; calculation does not round each purchase to a minimum tradable quantity.

Reading the chart and the cutoff date

The chart compares cumulative contributions with BTC value immediately after each monthly purchase and at the final valuation. Lines connect those observations; they do not reconstruct daily prices. They cannot measure the worst drawdown or show movements between purchases.

The final price is the close of the source's last complete daily candle, not a live quote. The file-generation time is shown separately. When our own system receives a newer valid JSON, the available months and cutoff update when the calculator is refreshed. No prices are invented to fill periods.

Source, limitations and privacy

The file identifies Binance BTC/USDT spot, UTC daily candles, as its source. Spot and perpetual-futures prices are not mixed. USDT is this series' quote asset; the tool does not convert USD into USDT or assume exact parity.

This is an idealized simulation: it excludes fees, taxes, slippage, bid–ask differences and minimum-amount or order-size restrictions. It does not model returns from lending BTC, custody or counterparty risks. A real purchase may have a different price and outcome.

The historical file stays private on the server. The page receives the results needed for display, not a JSON download link. We do not store the contribution or a calculation history. Turnstile verifies form use without receiving the amount or selected month; hosting may keep technical logs. Each result includes the source file's SHA-256 fingerprint.

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Educational tool, not personalized financial advice or a recommendation to buy BTC. Past performance does not guarantee future results; investment value can fall.