ERC-2981 Royalty Calculator

Recomputes an ERC-2981 royalty amount as floor(sale_price * royalty_fraction_bps / 10000) -- the same integer-division convention the OpenZeppelin reference ERC2981 implementation uses -- from a caller-declared sale_price and royalty_fraction_bps, using BigInt arithmetic throughout so a sale_price beyond Number.MAX_SAFE_INTEGER never loses precision. Flags a bps value above 10000 (100%) as out of range (the value the reference implementation reverts on) while still reporting the raw recompute, and compares against an optional claimed_royalty_amount. Zero network calls: this tool never queries a contract's actual royaltyInfo() return value -- sale_price, royalty_fraction_bps, and receiver are all caller-declared. Cross-links 528-nft-metadata-validator and 521-cant-be-evil-nft-license-picker for adjacent NFT-standard surfaces (metadata shape, license terms) this tool does not cover. ERC-2981 royalty payment is a voluntary off-chain convention: this tool makes no claim that any marketplace will actually pay the computed amount.

Tool URL: https://ainumbers.co/chaingraph/art-608-erc2981-royalty-calculator.html