Calculation rules v1.1 · Updated October 3, 2026
Reference price
BTCCost requests available public BTC quotes from CoinGecko, Coinbase and Kraken. When at least two sources respond, we use the median successful quote instead of treating one platform as the official Bitcoin price.
If only one source responds, the interface says “Single source.” If sources differ unusually, the interface reports a wider difference. If every source fails, no live price is shown and the converter offers a clearly labelled manual-price mode.
BTC and sats conversion
BTC amount = fiat amount ÷ reference BTC price
Fiat value = BTC amount × reference BTC price
Sats = BTC amount × 100,000,000
BTC and sats displays round to the nearest whole sat; valuations use the unrounded calculation. BTC ledger entries accept up to 8 decimals and are accumulated as integer sats. Quotes older than 2 minutes stop being used; a failed refresh is labelled explicitly. The timestamp indicates reference retrieval, not the time of an executed trade. Kraken does not offer a CNY pair in this tool.
True purchase cost
The true-cost tool treats the amount entered as the total budget. Percentage and fixed fees are removed first. The selected spread increases the assumed execution price above the independent reference price.
BTC received = (total budget − fees) ÷ execution price
Effective price = total budget ÷ BTC received
Cost premium = effective price ÷ reference price − 1
Planning scenarios
A goal calculation holds one user-selected BTC price constant so the amount is understandable. It does not forecast future prices or guarantee how much BTC a future purchase will receive.
Estimated target cost = remaining BTC × assumed price
Cost basis
The cost-basis tool uses the amount actually paid and BTC actually received. This naturally reflects any fees or spread already present in the transaction.
Average cost = total amount paid ÷ total BTC received
Profit or loss = current reference value − total amount paid
Percentage trading fees are calculated on the total budget, before fixed fees. If fees consume the budget, no BTC is received and effective price and premium are undefined. A worked check: $1,000 budget, $100,000 reference, 0.25% fee, 0.50% spread, $2 fixed fee → $4.50 direct fees, 990,547 sats displayed, about $100,954 effective price.