Probability itself is a standard field you do not create. What admins configure is the default probability tied to each opportunity Stage value, so the field populates sensibly as deals advance. You do this in the Stage picklist setup on the Opportunity object.
- Open the Stage field setup
In Setup, go to Object Manager, open Opportunity, choose Fields and Relationships, and open the Stage field. This is where each stage value and its settings live.
- Edit a stage value
Under Opportunity Stages Picklist Values, click Edit next to a stage such as Proposal or Negotiation. Each value has its own configuration row.
- Set the default probability
In the Probability field for that stage, enter the whole-number percentage that should populate when a deal reaches this stage. Base it on how often deals at this stage really close.
- Confirm the forecast category
On the same screen, check the Forecast Category mapped to the stage so probability and category tell a consistent story, then save.
- Validate on a test opportunity
Open or create a test opportunity, move it through the stages, and confirm the Probability and Expected Revenue fields update as expected.
The whole-number percentage written to the field when an opportunity enters this stage. Set per stage value.
The forecasting bucket (Pipeline, Best Case, Commit, Omitted, Closed) the stage maps to. Keep it aligned with the probability you chose.
Whether the stage counts as closed. Closed Won stages use 100 percent and Closed Lost stages use 0 percent.
- Changing a stage overwrites any manual probability a rep entered, so an override does not survive a later stage change.
- Removing the link between stage and probability stops the field updating automatically, which means reps must set probability by hand on every deal.
- Expected Revenue recalculates from Amount times Probability, so wrong defaults quietly distort weighted pipeline and forecasts.