MTTD calculator

Compare mean, median and range while keeping missing and excluded incidents visible.

Free to use. Save a file draft or explicitly enable storage on this device.

Current result

Mean Unknown min · Median Unknown min · 0 of 1 selected incidents included

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Review results

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Draft nameUsed in downloaded filenames.

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Inputs & calculation

Measurement contractDescribe which incidents belong in each period and how onset and discovery were established. These definitions keep the comparison interpretable.Offset for timestamps without a zoneFixed offset, not a daylight-saving rule. A pasted Z or ±HH:mm overrides it for that timestamp.

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Analysis filters

ServiceSeverityDiscovery methodReporting period

Mean Unknown min · Median Unknown min

0 included of 1 selected; 1 missing, 0 invalid, 0 excluded.

Other period: Unknown min mean, 0 included. Use the same scope in both periods; changed incident mix or missing timestamps can change the mean.

See individual durations and discovery methods

Each bar is one included incident; width is relative to the longest selected duration.

Discovery method	Included	Mean (min)	Missing
Unknown	0	Unknown	1

Incident records

All records remain editable below. Filters affect the report, not the stored draft.

Incident 1: Untitled · Current

Incident 1 fields

Incident labelImpact onsetFirst discoveryDiscovery methodServiceSeverityScope note / exclusion reasonPeriodExclude from calculation

Missing

Results

Review and export

This is incomplete or has review issues. You can save a draft; exports retain unknowns and warnings.

MTTD calculator report

MTTD calculator
User-entered draft; verify against source evidence.
Tool version 2 · https://aiopssre.com/mttd-calculator/
Name: Untitled

Offset for unzoned timestamps: UTC+00:00
Scope: [Not specified]
Filter: Current; service all; severity all; discovery all
Mean Unknown min; median Unknown min; range Unknown–Unknown min.
0 included / 1 selected; 1 missing, 0 invalid, 0 excluded.
Other period: mean Unknown min; 0 included. Compare only equivalent definitions and populations.
Unknown onset is missing, not zero. Undiscovered incidents cannot be counted by this calculator.

Incident	Onset	Discovery	Method	Service	Severity	Period	Excluded	Minutes	Scope note	Validation
						Current	false	Unknown		Missing

Why the mean and median differ

The mean gives every included detection duration a share of the total. The median identifies the middle duration after sorting. In the illustrative dataset, 5, 15 and 100 minutes produce a 40-minute mean and a 15-minute median: the longest delay pulls the mean upward. A fourth current-period incident has unknown onset, so it remains visible as missing rather than entering the calculation as zero.

Comparing reporting periods

The previous illustrative period has a 30-minute mean and a 20-minute median. The current mean is higher while the median is lower, so a single headline would conceal part of the change. Use the individual-duration view to find the long delay, then compare the service, severity and discovery-method filters across periods. Missing incidents still need investigation, and incidents never discovered are outside this dataset.

Read the accompanying guide · Source and further reading

Calculation and worksheet review: September 29, 2026.

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