Sales Forecast Calculator

Plan stock and cash against the peak.

Plan stock and cash against the peak. The peak month can be several times the average, and that is what stock and cash planning has to be sized against.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Currency

Current monthly revenue

Monthly growth

Months to forecast

Peak month

Peak month multiple

Current month

Revenue over 12 months

$1,801,321

$272,217 in the peak month

Starting monthly revenue$110,000

Ending monthly revenue$176,114

Peak month$272,217

Average month$150,110

The peak month is 1.8 times the average, which is what stock and cash planning has to be sized against. Forecasting on the average is how businesses run out of both in the month that matters most.

How the Sales Forecast Calculator works

The peak month can be several times the average, and that is what stock and cash planning has to be sized against. Forecasting on the average is how businesses run out of both in the month that matters most.

Also known as: revenue forecasting calculator · predict next quarter sales · sales projection model

Building a forecast that is worth having

A forecast built by applying a growth percentage to last year is arithmetic rather than forecasting. It carries no information about what will actually drive sales.

A useful forecast is built from drivers: traffic, conversion rate and average order value for a direct channel; units and price by product for a catalogue. Each driver can then be questioned individually.

The value is in the questioning rather than the output. A forecast that requires traffic to double is a forecast with a specific assumption in it, and identifying that assumption is what makes the forecast actionable. A single growth percentage hides it.

Seasonality, which has to be explicit

Most consumer businesses have a shape to their year, and an annual forecast divided by twelve describes no month that will actually occur.

Extracting the shape needs at least one full year of history and preferably two. Expressing each month as a percentage of the annual total gives a seasonal index that can be applied to a forecast total.

Two years lets you distinguish seasonality from one-off events. A spike in a single March could be seasonal or could be a promotion that ran once, and only a second year distinguishes them. Forecasting from one year of data reliably builds last year's accidents into next year's plan.

Three scenarios rather than one

A single forecast will be wrong, so the useful output is a range: a base case, a downside and an upside, with the assumptions that distinguish them stated.

The downside is the one that matters operationally, because it determines the cash requirement and the point at which costs have to be cut. A business that has only planned the base case has no plan for the case that requires one.

The upside matters too and is usually neglected. Growth faster than planned consumes cash for inventory, and businesses that stock out during an unexpectedly good quarter have failed to plan the upside as surely as if they had missed the downside.

Checking the forecast against reality

The discipline that improves forecasting is comparing forecast against actual every month and recording the variance.

Over a few months a pattern emerges, and it is almost always a consistent bias in one direction. Most small business forecasts run optimistic, frequently by 20% to 40%.

Knowing your own bias is more valuable than any individual forecast, because it can be applied as a correction to everything that follows. A business that knows it forecasts 30% high can plan on 70% of its forecast and be roughly right, which is considerably better than being consistently surprised.

What the forecast is actually for

Forecasts drive decisions rather than describing the future, and the decisions are specific: how much stock to order, how many people to hire, what to commit to.

Which means the forecast needs to be at the granularity those decisions require. A total revenue forecast does not tell you how many units of a particular SKU to order, and stock decisions are the ones that consume the cash.

It also means the forecast has to exist far enough ahead to be actionable. With a 90 day supplier lead time, a forecast produced monthly for the following month is useless for purchasing. The horizon has to exceed the longest lead time in the business, which for most importers means six months minimum.

Where to go next

The Sales Forecast question rarely arrives on its own. These are the ones that usually come with it:

Revenue Projection Calculator — Three inputs that multiply.
Monthly Revenue Goal Calculator — The growth rate the goal actually requires.
Cash Runway Forecast Calculator — The lowest balance is what matters.
Etsy Fee Calculator — Every Etsy fee on one sale, itemised.

Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price, check the platform's current fee schedule before you price a product against it. This is not tax or business advice.

Frequently asked questions

How do I forecast sales?

A baseline, a growth rate and a seasonal profile. The seasonal profile matters more than the growth rate for planning purposes, because it determines the peaks.

How do I build a seasonal profile?

From your own history, each month as a share of the annual total. Two or three years of data is enough to see the pattern; one year is a guess.

Should I forecast conservatively?

For cash, yes. For stock, forecasting low causes stockouts in the peak, which is usually the more expensive error. Two forecasts serving different decisions is not inconsistent.

How far ahead should I forecast?

Far enough to cover your lead time plus the selling season. For imported goods with a ten-week lead time, that means committing to peak stock five months ahead.