Lightning invoices and many retail BTC amounts are quoted in sats. Converting sats ↔ BTC before you pay reduces decimal mistakes.
Satoshi math is exact integer scaling: multiply BTC by 100,000,000 to get sats, or divide sats by the same factor to recover BTC. Explorers and wallets may still display truncated decimals — verify the full integer when amounts are large.
Pair unit conversion with address validation when you are sending on-chain BTC, and prefer a small test transfer when moving size to a new destination.