Sales Forecast Calculator – Project Future Revenue
Free Sales Forecast Calculator. Project future revenue based on growth rates and seasonality with confidence intervals.
Sales Forecast Calculator – Project Future Revenue
Free Sales Forecast Calculator. Project future revenue based on growth rates and seasonality with confidence intervals.
Generated: 2/22/2026, 12:34:35 AM | AskSMB.io
Sales Forecast Calculator
Project future revenue with confidence. Plan hiring, inventory, and cash flow based on realistic growth projections.
Inputs
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)
Results
Current monthly revenue must be greater than zero
How the Sales Forecast Calculator Works
Why Sales Forecasting Matters
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.
- Resource planning: Know when you can afford to hire, buy inventory, or invest in marketing
- Cash flow management: Predict when you'll need loans, lines of credit, or can make distributions
- Goal setting: Set realistic sales targets and hold teams accountable
- Investor confidence: Show investors you understand your business model and growth trajectory
- Strategic decisions: Evaluate whether to launch new products, enter new markets, or pivot
This calculator helps you create data-driven forecasts in minutes, with confidence levels so you know how much to trust the numbers.
How to Calculate Growth Rate
The most common forecasting mistake is using an inflated growth rate. Here's how to calculate it correctly:
Formula: Trailing 3-Month Growth Rate
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.
✅ Good Growth Assumptions
- Based on last 3-6 months actual data
- Accounts for churn and refunds
- Conservative (better to beat forecast)
- Specific to your business model
❌ Bad Growth Assumptions
- Based on your best month ever
- "If we just close 3 more deals..."
- Ignores historical variance
- Copied from another company's growth
Understanding Forecast Confidence
Not all forecasts are created equal. Confidence degrades rapidly as you forecast further out or assume aggressive growth:
✅ High Confidence (90% accuracy)
Timeframe: 1-3 months | Growth: 0-10% monthly | Use for: Hiring decisions, inventory orders, operational commitments
⚠️ Moderate Confidence (60-75% accuracy)
Timeframe: 4-12 months | Growth: 10-30% monthly | Use for: Annual budgeting, fundraising planning, strategic initiatives
⚠️ Low Confidence (40-60% accuracy)
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.
When and How to Include Seasonality
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.
Common Forecasting Mistakes to Avoid
- 1.Hockey stick syndrome: Forecasting flat growth then suddenly exponential. Real growth is gradual, not sudden. If you've grown 5%/month for 6 months, don't forecast 20% starting next month without a major initiative.
- 2.Ignoring churn: New revenue ≠ net revenue. If you close $10k in new deals but lose $3k to churn, your net growth is $7k. Always forecast net of cancellations.
- 3.Set-it-and-forget-it: Forecasts decay fast. Update monthly with actuals and adjust assumptions. A 6-month forecast you never revisit is useless by month 3.
- 4.Overweighting recent wins: One big deal doesn't change your growth trajectory. Base forecasts on averages, not outliers.
- 5.Assuming linear growth: Real business growth is lumpy. Factor in sales cycles, seasonality, and capacity constraints.
- 6.Ignoring macroeconomics: Economy entering recession? Budget cuts happening industry-wide? Factor in external headwinds.
What to Do With Your Forecast
A forecast is only valuable if you act on it:
- →Set hiring plans: If forecast shows $100k/month by Q3, and you need $80k/month to afford a new hire, plan recruitment for Q2.
- →Manage inventory: Forecast 30% growth into Q4? Order inventory now to avoid stockouts during peak.
- →Secure financing: Forecast shows cash crunch in 6 months? Apply for credit line now while you're profitable.
- →Set sales targets: Break down forecast into rep-level quotas and track weekly progress.
- →Evaluate initiatives: Compare actual vs forecast. If you launched a marketing campaign in month 3 and growth accelerated, it's working. If not, cut 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.
Example Calculation
Let's walk through a real-world example:
Scenario
Results
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
Confidence
⚠️ 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.
Frequently Asked Questions
Related Tools
💡 Quick Tips
- •All calculations happen in your browser - your data is private
- •Results update in real-time as you type
- •Export to PDF or share via link
- •No sign-up required