Raw pipeline adds up every open deal at full value, which always overstates what will close. Weighting corrects for that by discounting deals according to how far along they are. Early-stage deals count for a little; late-stage deals count for most of their value. The result is a rough expected value of the pipeline.
In HubSpot, each deal stage has a probability, set in the pipeline settings. The weighted amount on a deal is its amount multiplied by that probability, and reports can sum it across a pipeline, a team or a period. Because it depends on both properties, a deal with no amount contributes nothing, and a deal in a stage with a wrong probability contributes the wrong amount.
Weighted pipeline is only as good as the stage probabilities. If every stage is set to the default values and nobody has checked them against real win rates, the weights are guesses. If probabilities do not rise from one stage to the next, the weighting can make later deals look less likely than earlier ones. And deals that have stalled for months still carry their stage’s full probability.
Calibrate the probabilities once or twice a year using closed deals: of the deals that reached each stage, what share were eventually won? Use those numbers, and pair the weighted total with a check for stale deals so stalled opportunities do not inflate it.