About the Sales Forecast Calculator
This sales forecast calculator projects your revenue month by month. Start from your current monthly sales run rate, set an expected monthly growth rate, choose how many months to forecast and, if your business is seasonal, pick a seasonal pattern. You get total forecast sales, the final month’s revenue, the average month and the peak month, plus a chart and a monthly table.
Founders, small business owners and sales managers use it for budgets, hiring plans, inventory orders and loan applications. It is deliberately simple — a compound-growth trend multiplied by a seasonal index — so you can see how each assumption changes the outcome.
The current monthly sales figure should be your typical (de-seasonalised) month. Seasonal presets are generic indices that average 1.0 across the year: a holiday-retail pattern that peaks in November and December, and a summer pattern that peaks in June to August. Growth compounds every month, so 3% a month is about 42.6% a year.
With the default inputs, the total forecast sales is $730,889.52. Change any value above to recalculate instantly.
How to use the sales forecast calculator
- 1Enter your typical current monthly sales.
- 2Enter the monthly growth you expect (negative for decline).
- 3Choose how many months to forecast and the first calendar month.
- 4Pick a seasonal pattern if sales swing through the year.
- 5Review the total, the peak month and the monthly table.
Formula and method
Each forecast month starts from the current monthly sales run rate S₀ and grows it by the monthly growth rate g, compounded — month 1 is S₀ × (1 + g), month 2 is S₀ × (1 + g)², and so on. That is the growth trend.
The trend is then multiplied by the seasonal index for that calendar month. Indices average 1.0 over a year, so seasonality moves sales between months without changing the annual total much. With no seasonality every index is 1 and the forecast equals the trend. Change vs flat sales compares the forecast total with S₀ × months.
- S₀
- Current (typical) monthly sales
- g
- Monthly growth rate
- m
- Months from now (1, 2, 3…)
- Iₘ
- Seasonal index for that calendar month
Worked examples
$50k/month growing 3% a month for a year
Month 1 is $50,000 × 1.03 = $51,500 and month 12 is $50,000 × 1.03¹² = $71,288. The twelve months add up to about $730,890, roughly 21.8% more than twelve flat $50,000 months.
Holiday retailer growing 1% a month
The trend rises from $80,800 to $90,146, and the holiday index of 1.4 lifts December to about $126,204. The year totals about $1.03M.
Summer business, 6 months from April at 5% growth
April to September are forecast with a strong summer index. August is the peak at about $31,907 (trend $25,526 × 1.25), and the six months total about $165,848.
Frequently asked questions
How do you forecast sales for a small business?+
Start from recent monthly sales, apply a realistic growth rate based on history or pipeline, adjust for seasonal patterns, and review the forecast monthly against actual results. This calculator does the first three steps.
What is a realistic monthly sales growth rate?+
There is no universal figure, so base it on your own trailing 12–24 months of sales or your pipeline. For reference, 0.5% a month compounds to about 6.2% a year, 1% to 12.7% and 2% to 26.8%. Fast early-stage growth rarely lasts, so taper it in longer forecasts.
How do I convert monthly growth to annual growth?+
Compound it: annual growth = (1 + monthly rate)^12 − 1. For example 3% a month is 1.03^12 − 1 ≈ 42.6% a year, not 36%.
What is a seasonal index?+
A seasonal index shows how a month compares with an average month. An index of 1.25 means sales are typically 25% above average; 0.8 means 20% below. Indices across the year average 1.0.
How accurate is a sales forecast?+
Forecasts get less reliable the further out they go. Use this projection as a planning baseline, create optimistic and pessimistic versions by changing the growth rate, and update it as real results come in.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.