What needs to be finished first
Per item to estimate, acceptance criteria are available so effort can be anchored to a clearly bounded scope.
What needs to be ready before start
Estimation sheet with columns Item, Ideal Days, assumptions, dependencies; visible "Ideal Day" definition; list of reference items with Ideal Day values; timer.
One facilitator who keeps the definition consistent and collects values; the implementing team (2-9 people); a scribe for assumptions and caveats; optionally a PO for scope clarification.
Item list with acceptance criteria; Ideal Day definition (for example "8 h of focused work with no meetings, waiting, context switching"); two to three reference items from real delivery history with Ideal Day values.
15-60 min
Post the Ideal Day definition at the wall: "One day of focused work, no interruptions, no meetings, no blockers." Make reference items with values visible. Note that Ideal Day ≠ calendar day.
The one question this method answers
How many ideal days are needed for this item under focused work, and what assumptions about interruptions, dependencies, and uncertainty are made?
Marker: Phase
| Step | Duration | Action | Hint |
|---|---|---|---|
1Phase 1: Sharpen definition and references | 10 min | Review the Ideal Day definition together. Review reference items with values and adjust where needed. Record team consensus. | If someone says "my ideal day is 6 h, I have kids", the definition is too personal. Ideal Day is a methodological unit, not a real working day. |
2Phase 2: Estimate items | 20-30 min | Estimate items in ideal days as a team. Discuss large differences similarly to planning poker. Document assumptions (for example, "uses existing library X"). | If an item is larger than 5 ideal days, split it or run a spike first. Larger values are not reliable because assumption variability becomes too high. |
3Phase 3: Record dependencies and caveats | 10-15 min | For each item, make dependencies that could inflate calendar time explicit. Record caveats (for example, "requires review from external team", "compliance approval required"). | Ideal days without caveats are converted into calendar days. Caveats are a methodological safeguard against misinterpretation. |
4Phase 4: Apply calendar time factor | 5-10 min | For planning, translate Ideal Days into calendar time with an empirical factor (typically 1.5-3x). Derive the factor from team history and communicate a range rather than a single number. | If no historical factor exists, start with 2x as a conservative default and calibrate after 2-3 sprints. The factor is team-specific and changes with organizational context. |
What comes out at the end
Estimation table with columns Item, Ideal Days, assumptions, dependencies, caveats, derived calendar-time range. Ideal Day definition in the header. Linked with backlog and delivery history.
Keep Ideal Day values per item. Preserve old values as comments on re-estimations. Maintain the calendar-time factor centrally, with evidence from history (for example last 5 items with Ideal Day estimate and actual delivery time).
Compact working template for Ideal Days with context, input, output artifacts, and next step.
Estimates work in idealized work days without interruptions, meetings, or waiting time.
When and for what do we use this method?
Which data, observations, decisions, or materials are available?
Short notes along the runsheet.
Owner, date, and success signal.
Concrete filled scenario, fictional example
Concrete filled scenario, fictional example
Ideal Day definition: 8 h of focused work with no meetings, waiting, context switching. Team calendar-time factor: 2.5x (history from the last 5 items with Ideal Day estimate and actual delivery time).
| Item | Ideal Days | Assumptions | Calendar time |
|---|---|---|---|
| API endpoint for tenant export | 2 | uses pagination helper, JSON+CSV | 5 days |
| DATEV import validation | 3 | library fits, sample data available | 7-8 days |
| Recommendation prompt in dashboard | 1 | UI component exists, only logic is new | 2-3 days |
| Webhook system baseline | 4 | new infrastructure, compliance review required | 10-12 days |
Caveats
Factor calibration: last 5 items had Real/Ideal ratios between 2.1 and 2.8. Mean 2.5 for current planning. Revisit after Sprint 23.
Recognize symptoms and steer against them
Stakeholders or PMs read "3 Ideal Days" as three working days.
Communicate calendar-time factor consistently: "3 Ideal Days = 7-8 calendar days." Put the definition in each estimation document. Any statement using only Ideal Days invites misinterpretation.
The team has used factor 2x for two years while reality is now 3.5x.
Recalculate the factor every sprint or quarter from the last 5-10 items. If factor exceeds 3x, check whether ideal conditions are unrealistic or where organizational bottlenecks have increased.
The discussion "my ideal day is 6 h" shifts the scale and makes estimates incompatible.
Treat the definition as a methodological constant (typically 8 h of focused work). Do not adapt it to personal realities, otherwise compareability is lost.
The table has Ideal Day values but no assumptions, so re-estimation is not possible.
Assumptions are required per item. Without assumptions, estimates are not reproducible and not verifiable.
Items above 8 Ideal Days stay in the list and estimation accuracy drops sharply.
Split items over 5 Ideal Days or put a spike first. Large estimates have too many assumptions, and variance becomes unmanageable.
Done signals checkable in under a minute
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