When SQRT rounds twice
SQRT is rounded twice, once to 64 bits and once to 53
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The Handbook of Excel Functions
What Excel functions do. How they work. Where they surprise you.
A practical reference for using and implementing Excel functions, with runnable formulas, numerical quirks and differences between versions.
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From the measurement record
ROUND counts digits in 32 bits, and the count wraps
Excel's recorded answer
00x0000000000000000Mathematical value
-1125000000000000xc2d9945ca2620000ROUND(-112500000000000, 2147483635)
Excel 16.0 build 20430, Windows 64-bit, CPU not recorded in this capture
A payment formula's arithmetic
PMT takes ln(1+rate) from a series, and stores its quotient before the rate
The documented formula differs
For bills longer than 182 days TBILLEQ is a quadratic, not the documented formula
One build, conflicting answers
WEEKNUM with an invalid return_type can answer differently each time it is called
For engine builders, auditors, and the numerically curious
Start with a function's call signature, read the recorded surprises, or follow the research behind an algorithm.
Where Excel's answer is inaccurate · The Last Bit
The Last Bit Article
374 entries match every recorded Excel answer in our Rust implementation. See every state →
554 of 554 entries have curated prose files; 0 have projection-only pages. 554 entries = 531 functions + 23 operators = 534 published Excel rows + 7 split byte-variant rows + 13 added functions. Read the coverage and limits →