Free Sales Forecast Calculator. Project future revenue based on growth rates and seasonality with confidence intervals.
Free Sales Forecast Calculator. Project future revenue based on growth rates and seasonality with confidence intervals.
Generated: 1/13/2026, 7:21:13 AM | AskSMB.io
Project future revenue with confidence. Plan hiring, inventory, and cash flow based on realistic growth projections.
Your current or most recent month's revenue
Expected monthly revenue growth (use trailing 3-month avg)
How many months to forecast (1-60)
Seasonal adjustment (+20% for peak, -15% for slow months)
Current monthly revenue must be greater than zero
Sales forecasting is the foundation of business planning. Without accurate forecasts, you're flying blind—hiring too early or too late, running out of inventory or over-ordering, missing cash crunches or leaving money idle.
Yet most SMBs either don't forecast at all (32% according to studies) or use overly optimistic gut-feel estimates that consistently miss by 30-50%. The result: cash flow crises, missed growth opportunities, and reactive decision-making.
This calculator helps you create data-driven forecasts in minutes, with confidence levels so you know how much to trust the numbers.
The most common forecasting mistake is using an inflated growth rate. Here's how to calculate it correctly:
Growth Rate = (Month 3 - Month 1) / Month 1 / 2 months
Example: ($55k - $50k) / $50k / 2 = 5% monthly
Why trailing 3 months? It smooths out volatility from one-time events (big deal closed, refund issued) while being recent enough to reflect current trajectory. Don't use your best month or "we could grow 20% if everything goes right" thinking.
Not all forecasts are created equal. Confidence degrades rapidly as you forecast further out or assume aggressive growth:
Timeframe: 1-3 months | Growth: 0-10% monthly | Use for: Hiring decisions, inventory orders, operational commitments
Timeframe: 4-12 months | Growth: 10-30% monthly | Use for: Annual budgeting, fundraising planning, strategic initiatives
Timeframe: 12+ months | Growth: 30%+ monthly | Use for: Vision planning, directional guidance only—do not commit resources
Pro tip: Create three forecasts: conservative (70% chance), baseline (50% chance), and optimistic (30% chance). Plan resources based on conservative, celebrate if you hit optimistic.
Seasonality is predictable revenue variation based on time of year. Include it if your business has consistent patterns:
| Business Type | Peak Months | Typical Variance |
|---|---|---|
| Retail / Ecommerce | Nov-Dec (holidays) | +40% to +60% |
| B2B Software | Q4 (budget flush) | +25% to +35% |
| Tax/Accounting | Jan-Apr (tax season) | +50% to +80% |
| Travel/Hospitality | Jun-Aug (summer) | +30% to +50% |
| SaaS/Subscriptions | Minimal seasonality | ±5% to ±10% |
To calculate your seasonality factor: Compare each month's revenue to your 12-month average. If December is typically 50% above average, use +50%. If February is 20% below, use -20%. Only use seasonality if you have at least 12 months of historical data.
A forecast is only valuable if you act on it:
Monthly review ritual: Compare actual vs forecast. Calculate variance (%). If variance >20%, identify root cause (deals slipped, churn spiked, pricing change). Update next month's forecast based on new data.
Let's walk through a real-world example:
Month 1: $50,000
Month 6: $63,400 (27% growth)
Month 12: $79,600 (59% annual growth)
Total 12-month revenue: $819,000
Average monthly: $68,200
⚠️ Moderate Confidence
12-month forecast with 5% monthly growth. Expect 15-25% variance from actuals. Review quarterly and adjust assumptions as needed. Use for annual planning but update monthly.