How do you estimate work using story points?
Story points estimate relative size, not time. They combine effort, complexity and uncertainty compared with other backlog items.
I use planning poker. The team discusses each item, asks clarifying questions, and simultaneously reveals a card from a sequence such as Fibonacci. Disagreement is useful because it surfaces hidden assumptions, so I ask the highest and lowest estimators to explain their thinking. We re vote until we converge, without forcing false consensus.
I anchor estimates with a reference story the team agreed on. A three point story is roughly three times the size of a one point story, but that says nothing about hours.
Points are for the team's own forecasting, not for comparing teams or measuring individual productivity. Velocity is a rough guide for how much to take into a sprint, and it should never be used as a performance target.