How it works
How to forecast your sales
Enter your current revenue
Start with your current monthly or annual revenue. Use a recent number that represents your normal run rate, not a one-off spike month.
Set your growth rate and time period
Enter the monthly or annual growth rate you expect and how far out you want to forecast. The calculator supports both linear growth (same dollar amount each period) and compound growth (percentage-based).
Review the projection
You get projected revenue for each period plus the total over the forecast window. Use it for budgeting, hiring plans, or investor conversations. Just remember that forecasts are estimates, not guarantees.
Tips for more accurate forecasts
Forecasts are only useful if they are grounded in reality. Here is how to keep them honest.
Use trailing 3-month averages
Don't base a forecast on your best month ever. Average the last 3 months to smooth out spikes and dips. If you did $22k, $28k, and $25k, start with $25k as your baseline.
Account for seasonality
Most ecommerce businesses do 25% to 40% of annual revenue in Q4. A straight-line forecast will overestimate spring and underestimate holiday season. Adjust your monthly growth rates if you know seasonal patterns.
Choose the right growth model
Compound growth works for businesses in a growth phase where more customers bring more word-of-mouth and reviews. Linear growth fits mature businesses that add a steady number of new customers each month.
Run best-case and worst-case scenarios
Create three forecasts: optimistic, realistic, and conservative. If your realistic growth is 10%, run it at 15% and 5% too. Plan spending based on the conservative number and treat the upside as a bonus.
Update monthly with actual numbers
A forecast set in January and never updated is useless by April. Each month, compare actual revenue to forecast and adjust your growth rate. This keeps the projection connected to reality.
Be skeptical of high compound rates
Growing 15% month-over-month sounds great, but that compounds to 435% annual growth. Very few businesses sustain that for a full year. If your forecast shows revenue 5x-ing in 12 months, double-check whether that is realistic for your market.
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Questions, answered
Linear growth adds the same dollar amount every period. If you grow by $2,000 per month, you go from $20,000 to $22,000 to $24,000. Compound growth applies a percentage, so each period grows from the new total. At 10% monthly, $20,000 becomes $22,000, then $24,200, then $26,620. Compound growth accelerates over time.
Honestly, not perfectly accurate. They're educated guesses based on current trends. A forecast 1 to 3 months out is usually pretty reliable. Beyond 6 months it gets fuzzy. The value isn't in nailing the exact number but in having a reasonable target to plan around.
Look at your actual month-over-month growth from the past 6 months. If you've been growing at 7% per month consistently, that's a reasonable starting point. Don't use your best single month. Average it out and maybe knock it down a point or two to be safe.
Monthly for operational planning and cash flow. Annual for bigger strategic decisions like hiring and inventory. If you're doing under $500,000 a year, monthly forecasts help you catch problems early. At $2 million plus, you probably want both views.
Don't use a flat growth rate across all months. If you know December does 3x your average month, adjust that month's figure manually. Some stores do 35% of their annual revenue between Black Friday and Christmas. A flat forecast would miss that entirely and either overcount or undercount depending on the month.
That's a decline forecast, and it's still useful. If you're losing 3% per month, the calculator shows where revenue ends up if nothing changes. A store doing $40,000 a month declining at 3% monthly drops to about $28,400 in 12 months. Sometimes seeing that number is the wake-up call you need to change course.
You can, but with a big grain of salt. Without historical data you're really just guessing at the growth rate. Start with conservative assumptions. If you expect $5,000 in month one, forecast 5% to 10% monthly growth and see what that looks like. Adjust after you have 3 months of real data.
For most ecommerce stores, 6 to 12 months is the sweet spot. Forecasting beyond a year gets unreliable because too many things change: market conditions, competition, your own strategy shifts. A 12-month forecast updated monthly gives you enough runway without pretending you can predict the future.
Grow with reviews that compound
Every review you collect makes the next sale easier. WiserReview helps you build a steady stream of customer reviews that drive organic growth and make your sales forecast a number you can actually hit.
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