# The Handbook of Excel Functions

Canonical open reference for Excel functions and operators.

- Catalogue: https://handbook.dnacalc.com/api/index.json
- Function page: https://handbook.dnacalc.com/functions/ROUND.html
- Stable function JSON: https://handbook.dnacalc.com/api/functions/FUNC.ROUND.json
- Schema: https://handbook.dnacalc.com/api/function-reference.schema.json
- Evaluation: POST https://handbook.dnacalc.com/api/eval with {"formula":"=ROUND(1.005,2)"}
- Contributions: POST https://handbook.dnacalc.com/api/contributions

Replace ROUND with the case-sensitive function name, including dots; use operator IDs such as OP_ADD. All catalogue IDs resolve. JSON contains section_order, sections (Markdown), try_it, versions (Excel build and platform), implementations (language and suite), variants (difference, error_bound, onecalc_udf, and for recorded Excel environments excel_build_range, cpu, state, code and evidence), implementation_state (what we conclude about our own Rust, with counts) and sources. Pinned source snapshots use flavour excel-compatibility-candidate and suite null until admitted against a published Handbook suite. Empty lists mean no records, not proof of identical behaviour. OneCalc results are not Excel measurements. API errors and engine refusals must be preserved.