How to Build a Weighted Sales Forecast in a Spreadsheet

“We’ll probably hit target” isn’t a forecast. A weighted forecast is — and you can build one in a free sales forecast spreadsheet without a CRM.

The one idea: weight by probability

Each deal gets a close probability based on its stage. The forecast is the sum of every deal’s value × its probability:

• Discovery → 20%
• Proposal → 50%
• Negotiation → 80%
• Verbal yes → 90%

A $10,000 deal at 50% contributes $5,000 to the forecast. Sum that across the pipeline and you have a realistic number, not a best-case dream.

Build it in four columns

1. Deal value — the full contract amount.
2. Stage — drives the probability.
3. Probability — looked up from your stage table.
4. Weighted value — =deal_value * probability.

Then =SUM(weighted_value_column) is your forecast. Add a close-month column and a SUMIFS to roll it up by month or quarter.

Make it honest

• Calibrate the percentages against your real win rates per stage, then trust them.
• Show best-case vs. committed — committed = deals at 80%+; best case = everything weighted. The gap is your risk.
• Update stages weekly. A forecast is only as good as the last time someone moved the deals.

When forecasting becomes a daily, multi-user job, that’s when a CRM’s automation earns its cost — but the math above is exactly what it’s doing under the hood.

These templates are operational tools, not financial guidance.