Sales Forecast Calculator
Build a bottoms-up revenue forecast from your actual base. Account for every customer you lost, every one you added mid-year, your pipeline, and the macro factors that move the number.
Forecast Period
How many months are you forecasting?
Prior Period Revenue
Your total revenue for the last full period — the baseline everything is measured against.
Known Lost Customers
Customers you know you've lost or will lose. Revenue is prorated — a customer lost in month 3 costs you 9 months of revenue, not 12.
Mid-Period New Customers
Customers already won this period. Revenue is prorated from the month they came on board — a customer acquired in month 4 contributes 9 months of revenue.
New Customer Pipeline
Prospects not yet closed. Each deal is probability-weighted and prorated from expected close month. A $100K deal at 60% closing in month 6 contributes $35K to a 12-month forecast.
Rate Adjustments
Applied to your retained customer base. Use negative values for declines.
Organic volume change
Cost pass-through
Deliberate price action
Forecast Result
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Enter your prior period revenue above to see your forecast.
Need help building a defensible forecast?
A fractional sales manager can build the forecast model, run the pipeline review, and hold the team accountable to the number.
Talk to LeamanHow the math works
Retained base
(Prior revenue − lost customer annual value) × (period months / 12)
The revenue you can count on from customers you're keeping, scaled to the forecast period.
Lost customer impact
(Annual revenue / 12) × months remaining after loss month
You don't lose the full year — only the months after they left. A customer lost in month 3 costs 9 months of revenue.
New customers (mid-period)
(Annual revenue / 12) × months active from acquisition month
A customer acquired in month 4 contributes 9 months of revenue in a 12-month period.
Pipeline (probability-weighted)
(Annual revenue / 12) × months active from close month × close probability %
Each deal is discounted by its probability and prorated from expected close. A $100K deal at 60% closing in month 6 = $35K.
Run rate adjustment
Retained base × run rate change %
Applied to the retained base only. Captures organic volume changes in existing accounts.
Inflation & price increase
Retained base × rate %
Both applied to retained base. Inflation = cost pass-through. Price increase = deliberate action. They stack.
Related Tools & Resources
Pipeline & Capacity Planner
Check pipeline coverage and model whether your team can hit the number
CRM Stage Exit Criteria
Clean pipeline data is the foundation of a reliable forecast
Sales Weekly Meeting Agenda
The cadence where forecast assumptions get tested weekly
Sales Playbook Builder
The process that generates the pipeline this tool forecasts
Sales 1-on-1 Meeting Framework
The weekly coaching meeting where pipeline assumptions get pressure-tested
Sales Hiring Scorecard
The rep capacity behind your forecast depends on who you hire
Sales Coaching Plan
Develop the reps who are responsible for hitting the number
Fractional Sales Manager
Get the forecast built and the pipeline reviewed for you
How to Improve Forecast Accuracy
The behaviors and processes that make forecasts reliable
Sales Leadership Operating System
The full SLOS hub — all tools in one place