Quick answer: A cash flow forecast spreadsheet needs four core columns — date, description, amount, and running balance — with every expected inflow and outflow listed as its own row on its own date, sorted chronologically, and a running balance formula carried down the full sheet.
What spreadsheet program works best for this?
Any standard spreadsheet application with basic formula support (a simple addition/subtraction running total) is sufficient — no specialized financial software is required.
How do I handle multiple bank accounts in one forecast?
Either build a separate forecast per account, or add an account column and combine per-account running balances into a master total, depending on how you actually manage money across accounts.
Setting up the core structure
Column A: date. Column B: description (e.g., 'Rent,' 'Paycheck — Employer Name'). Column C: amount, entered as a negative number for outflows and a positive number for inflows. Column D: running balance.
Row 1 should be your actual current balance as of today, with every subsequent row representing a future expected transaction.
The one formula that does all the work
In the running balance column, each row's formula is simply: previous row's balance + current row's amount. Copied down the entire sheet, this produces a continuously updating projected balance for every single date.
Conditional formatting to highlight any negative balance in red makes cash flow gaps immediately visible without needing to scan the numbers manually.
Populating it with real data
List every known recurring income and expense for the next 90 days first, using real historical dates as a guide for when each one typically lands.
Add known irregular expenses (insurance premiums, annual fees, seasonal costs) on their specific expected dates.
Sort the full list chronologically by date before finalizing the running balance column, since the formula depends on rows being in correct date order.
Frequently Asked Questions
What spreadsheet program works best for this?
Any standard spreadsheet application with basic formula support (a simple addition/subtraction running total) is sufficient — no specialized financial software is required.
How do I handle multiple bank accounts in one forecast?
Either build a separate forecast per account, or add an account column and combine per-account running balances into a master total, depending on how you actually manage money across accounts.
Is a spreadsheet as effective as a dedicated tool?
A well-built spreadsheet can capture the same core logic as a dedicated forecasting tool — a dedicated tool mainly saves setup time and automates the chart and score calculations.