DUR2MILLISECONDS Function in Apple Numbers: Syntax, Examples and Troubleshooting

• Introduced: Documented in Apple’s Formulas and Functions Help 15.4; the original introduction release is not established.
• Availability: Supported by the current Apple Formulas and Functions Help 15.4 documentation for Numbers; no final supported-version endpoint is identified.
• Scope: Shared iWork function reference; the formatting steps below refer to Numbers for Mac. Older releases and individual-client introduction dates are not established here.
• Checked: October 14, 2026, against the official DUR2MILLISECONDS reference. Documentation and independent arithmetic checks; no native Numbers test.

=DUR2MILLISECONDS(duration)

duration is the single required argument: an elapsed-time value, or a reference to a cell containing one. There is no optional conversion mode or documented default input. The output is a number of milliseconds, rather than another duration value. Apple describes the input type in its argument and value guide.

For predictable practice data, create the duration with DURATION instead of relying on how a colon-separated text entry is interpreted. A bare number such as 1.5 does not state whether you mean days, hours or minutes; put it in the correct DURATION argument first. The formulas here use English-language commas and decimal points; use the function editor’s local syntax if your document uses different separators.

Create a Numbers table with at least six columns and eleven rows. Use A1 for Description, B1 for Duration and C1 for Total milliseconds. Enter the following formulas in B2:B7; do not type them as quoted text.

In C2, enter =DUR2MILLISECONDS(B2) and fill down through C7. C3 should refer to B3, and so on. Set C2:C7 to Number, with enough decimal places to inspect small results. Values marked ≈ are rounded here for display, not instructions to round the stored result.

A duration can exceed a day and can be negative. The negative row represents a signed time adjustment; the zero row is an explicit zero duration, not an empty cell. Do not replace the required argument with a blank and assume the same behavior.

One second corresponds to 1000 milliseconds. Add each component after expressing it in milliseconds; the conversion does not discard whole seconds, minutes or days. This dimensional calculation is independent of a cell’s chosen display style.

In B10, enter =DURATION(0,0,0,0,1,250). This represents an observed latency of 1.25 seconds. Type the numeric threshold 800 in D10, meaning 800 milliseconds, and enter =DUR2MILLISECONDS(B10) in C10. The expected output is 1250.

In E10, use =C10-D10; the excess is 450 milliseconds. In F10, enter =C10/D10; the ratio is 1.5625, or 156.25% of the threshold. The ratio has no time unit, because milliseconds cancel milliseconds.

Keep the threshold numeric and label its unit in the header. Comparing 1250 directly with a threshold typed as 0.8 seconds would introduce a factor-of-1000 error. This function converts a recorded duration; it does not measure a computer’s timing precision or prove that an imported observation is accurate to one millisecond.

• The result seems to lose precision: show more decimal places. On Mac, select the result cell, open Format > Cell, choose Number, and adjust Decimals. Apple’s formatting guide explains that displayed rounding does not change the value used in subsequent calculations.
• The input is a clock time: a date/time value and an elapsed duration are different types. Use TIME for a time of day, or construct the elapsed quantity with DURATION. Do not infer duration units from how a clock-style string looks.
• The formula is rejected: check the function spelling, the one required input, and whether B2 contains a real duration-producing formula. The function page does not enumerate exact error labels for every invalid text, missing argument or out-of-range case, so no particular error code is promised here.
• A downstream calculation fails: inspect its denominators and unit labels before wrapping it in IFERROR. Hiding an error does not fix an input expressed in the wrong unit.

The examples use exact millisecond arithmetic. Undocumented input coercion and precision limits remain unverified; displayed decimal places alone do not establish those limits.