Frame the time problem correctly
Calculate successor timing from dependency relationship, duration, lead, or lag.
The Dependency Lead/Lag Calculator addresses dependency lead/lag: it is designed to calculate successor timing from dependency relationship, duration, lead, or lag. For this planning case, define the particular contract, project, invoice, workflow, or reporting period; a date borrowed from one case and a duration borrowed from another can still produce a plausible but irrelevant answer.
For the selected roster, the practical scope of dependency lead/lag is deliberately narrower than the surrounding operational decision. For dependency lead/lag, a modeled path or forecast describes the entered dependency network, not guaranteed delivery performance. For the schedule owner, treat Predecessor starts as the anchor and keep Successor duration (days) tied to that same source scenario.
Input review
Input quality matters more than extra decimals
For the documented baseline, the dependency lead/lag calculation draws on Predecessor starts, Predecessor duration (days), Relationship, and 2 additional fields. In the source worksheet, capture the dependency lead/lag entries from one source version before experimenting with alternatives. For the saved baseline, retain the zone of each timestamp, the calendar convention for every date, and the stated unit of each duration or percentage.
- Predecessor starts for dependency lead/lag: Enter the calendar date for Predecessor starts; use the local date that governs this calculation.
- Before calculation, predecessor duration (days) for dependency lead/lag: Enter Predecessor duration (days) in days and keep that unit consistent with the other duration fields.
- Relationship for dependency lead/lag: Choose the Relationship option that matches the rule or record being modeled.
- In the source worksheet, lag days (negative is lead) for dependency lead/lag: Enter Lag days (negative is lead) in days and keep that unit consistent with the other duration fields.
- For a consistent scenario, successor duration (days) for dependency lead/lag: Use the Successor duration (days) value stated in days; do not mix it with a differently scaled duration.
While checking the entries, read Predecessor starts together with Successor duration (days) rather than validating each field in isolation. For the entered case, a correct-looking number can describe the wrong case when an anchor is transposed, a duration changes units, or an exclusion belongs to another calendar.
Method
The rule used by this calculator
The predecessor finish is calculated first. The selected finish-to-start, start-to-start, finish-to-finish, or start-to-finish relationship anchors the successor.
Before rounding the output, connect each displayed operation to its named field. For the calculation path, preserve unrounded intermediate values for dependency lead/lag; if the result represents complete days, stages, cycles, or work items, decide whether the real planning rule permits a fraction or requires a stated rounding convention.
During the arithmetic check, a useful dependency lead/lag arithmetic check holds every entry constant except Successor duration (days). In the unrounded work, the revised dependency lead/lag output should move in a direction that agrees with the role of that field; an unexpected movement usually points to a unit, sign, or boundary mistake.
Verification
Independent checks for the schedule
At the exception review, review the dependency lead/lag result independently of the calculate button. Before accepting the result, use the source record to estimate direction and scale, then compare that expectation with the displayed date, duration, path, capacity, or bucket.
- During verification, reconcile Predecessor starts with the source record before calculating.
- For the reasonableness review, verify the unit and meaning of Predecessor duration (days) rather than relying on its numeric size.
- A separate dependency lead/lag check should trace predecessor logic and duration units before accepting the final date.
- Before accepting the result, change Successor duration (days) by one controlled increment and confirm the dependency lead/lag result moves in the expected direction.
While reconciling the schedule, if a dependency lead/lag check fails, preserve the entered case instead of forcing the answer to match. In a separate review, identify the dependency lead/lag assumption that differs from the source and rerun the Dependency Lead/Lag Calculator only after correcting that field.
Interpretation
Understanding the output hierarchy
Interpretation The result models one dependency pair. Negative lag represents lead time and can create intentional overlap. Validate the Dependency Lead/Lag Calculator deadline separately from Successor duration (days); internal buffers remain adjustable unless the entered scenario fixes them.
The Dependency Lead/Lag Calculator timeline models checkpoints from Predecessor starts, Predecessor duration (days), Relationship, Lag days (negative is lead), and Successor duration (days). Validate Successor duration (days) from the anchor toward the horizon carrying the consequence.
Before carrying the figure forward, describe the answer as a dependency lead/lag result and name its time basis, anchor, and governing scenario. Beside the headline, this prevents the dependency lead/lag figure from being mistaken for an approval, compliance finding, entitlement, or delivery guarantee.
Worked case
Work through the default scenario
Worked scenario Example: A finish-to-start relationship with a two-day lag places successor start two days after predecessor completion. Cross-check the Dependency Lead/Lag Calculator control event with Predecessor starts and Predecessor duration (days), then validate each Successor duration (days) adjustment.
Before entering live figures, rebuild the dependency lead/lag example once with the published defaults. For dependency lead/lag, write down the anchor, the intermediate relationship, and the output unit; then alter a single entry so the reason for the changed answer remains visible.
The worked dependency lead/lag case demonstrates how to calculate successor timing from dependency relationship, duration, lead, or lag, but it is not a ready-made project or deadline. While checking the default case, replace every dependency lead/lag sample value with the actual record before using the Dependency Lead/Lag Calculator result in a schedule, notice, forecast, or approval workflow.
For a separate operational check, use the Critical Path Timeline Calculator; it is designed to find the longest dependent task chain and earliest project completion.
Separate the calculation from the decision
At the interpretation boundary, the Dependency Lead/Lag Calculator answers one defined question about dependency lead/lag. Because this is a dependency lead/lag model, a modeled path or forecast describes the entered dependency network, not guaranteed delivery performance. For the adjacent question, a nearby page may use the same dates while measuring something else, so compare it with the dependency lead/lag result by output meaning rather than by which number looks more conservative.
When comparing nearby tools, before transferring a dependency lead/lag result, write one sentence naming its anchor, period, and intended decision. When naming the output, if the dependency lead/lag statement claims approval, compliance, entitlement, or guaranteed delivery, it has moved beyond this calculator's scope.
Recordkeeping
Make a later rerun possible
Before archiving the result, a later reviewer should be able to reproduce the dependency lead/lag result without guessing. Store these items with the output:
- Predecessor starts
- Predecessor duration (days)
- Relationship
For reproducibility, also retain the calculation timestamp and the version of any calendar, dependency list, policy, or workflow assumption used. In the audit trail, mark superseded dependency lead/lag runs as historical instead of silently replacing them.
An operational use for the result
Practical use Confirm relationship semantics in the project plan and test whether overlap is operationally possible.
The practical use of this page is to calculate successor timing from dependency relationship, duration, lead, or lag. For the next scheduling decision, keep the dependency lead/lag result beside the contract, project plan, work-item history, invoice, calendar, or approval record it informs so its assumptions remain visible.
In the operational workflow, when Predecessor starts or Successor duration (days) changes, save a new dependency lead/lag run rather than overwriting the old one. In the working plan, a side-by-side dependency lead/lag comparison then shows whether the changed conclusion came from the anchor, a duration, an exclusion, or a policy decision.
Boundaries
What still requires policy or human judgment
Business calendars, partial completion, multiple predecessors, resource limits, and nonworking dates are excluded. Refresh the Dependency Lead/Lag Calculator allowance when Successor duration (days) differs from the entered scenario rule; model its dependent checkpoints again.
Where the inputs stop, use the Dependency Lead/Lag Calculator as transparent dependency lead/lag arithmetic, not as a substitute for the controlling agreement, approved project plan, official calendar, financial record, or responsible reviewer. When an exception appears, resolve material dependency lead/lag discrepancies before distributing the result.
What people ask about dependency lead/lag
What is the difference between lead and lag?
Lag inserts waiting time; lead permits the successor to begin before the normal dependency boundary.
Which inputs make a dependency lead/lag calculator result reproducible?
Another reviewer needs Predecessor starts and Predecessor duration (days) and Relationship, Lag days (negative is lead), and Successor duration (days) to recreate the Dependency Lead/Lag Calculator. Store those values with their units and generation date.
What event should trigger another dependency lead/lag calculator calculation?
Reconsider the Dependency Lead/Lag Calculator when Successor duration (days) no longer matches the source used for Predecessor starts. In the context of dependency lead/lag, a new calculation keeps the cases separate.
Can an error in Predecessor starts shift the dependency lead/lag calculator output?
Predecessor starts supplies the controlling Dependency Lead/Lag Calculator boundary; Successor duration (days) changes a dependent checkpoint or allowance. Validate that Successor duration (days) allowance before moving the horizon.