Cash Flow Forecast Calculator

How it is calculated

The forecast assumes the same income and the same expenses every month, so the balance moves in a straight line:

net per month = income − expenses
total net = net per month × months
ending cash = starting cash + total net

Amounts are shown in dollars with two decimals; a negative result carries the minus sign before the currency symbol, such as -$900.00. Income and expenses are money flowing in and out, so neither may be negative; only the starting balance can be negative (an overdraft). The number of months must be at least 1 and may be fractional, such as 2.5. The tool does not model growth, seasonality, late-paying customers, tax dates or one-off payments, and it does not stop at zero, so a negative ending balance simply means the account would be overdrawn.

Common mistakes

• Typing a gross figure for income and a net one for expenses, or the reverse. Both lines must be on the same footing, either before tax or after tax.
• Entering expenses as a negative number. The tool subtracts expenses itself, and a negative expense (or negative income) is rejected, so you get no result instead of a forecast.
• Using one average month for a business with uneven months. Rent due in January and a big invoice paid in March both vanish into the average, so the monthly curve may dip below zero even if the end figure looks fine.
• Forgetting one-off costs such as tax, annual insurance or equipment. Only the recurring monthly gap is modelled, so add one-offs to the expense figure or subtract them from the starting cash.
• Entering a number of months below 1, for example 0.5 for a two-week view. The tool needs at least one month and shows nothing for less.