Weighted pipeline equals the sum, across all open opportunities, of deal value multiplied by the probability assigned to that deal's stage.
The only difficult input
The arithmetic is trivial and the probabilities are not. A stage probability should be the observed proportion of opportunities that reached that stage and eventually closed won, calculated from your own history over a period long enough to contain a reasonable number of outcomes, and calculated separately for each distinct sales motion. Default percentages supplied with software are round numbers chosen for tidiness, and a weighted total built on them is arithmetic performed on fiction.
A worked example (illustrative figures)
Four open deals. Deal A, ₹10,00,000, at qualification, historic conversion 10%, contributes ₹1,00,000. Deal B, ₹6,00,000, at discovery, 25%, contributes ₹1,50,000. Deal C, ₹8,00,000, at proposal, 50%, contributes ₹4,00,000. Deal D, ₹4,00,000, at negotiation, 75%, contributes ₹3,00,000. Raw pipeline is ₹28,00,000. Weighted pipeline is ₹9,50,000. Now consider a second team with the same ₹28,00,000 raw total, but with ₹20,00,000 of it at negotiation. Their weighted figure would be far higher, and the two teams are in genuinely different positions despite identical headline pipelines. That comparison is the thing weighting is good for.