Dr. Paul Borosky, DBA, MBA
Business Consultant & Author
Guide 10 of 11 · Manage Cash
How to Make a 13-Week Cash Flow Forecast
Your bank balance shows today. This shows February.
Every other report looks backward. The 13-week cash forecast looks forward, one week at a time, to the lowest balance coming in the next quarter. It takes an hour to build and 20 minutes a week to keep, and it turns a bad Monday into ten weeks of warning.
Last Updated: 10/27/2026 · Written by Dr. Paul Borosky, DBA, MBA
The Short Answer
What Is a 13-Week Cash Flow Forecast?
Textbook Definition
A 13-week cash forecast is a week-by-week estimate of the cash coming into and going out of a business for the next 13 weeks, one quarter, and the bank balance expected at the end of each week.
In Plain English
A simple table that tells you whether you will make payroll in February, while it is still December. Count collections, not sales. Find the lowest week. If it is below your floor, act now.
Each Week
Starting cash + cash in − cash out = ending cash
Next week starts with this week’s ending cash
Your floor is the minimum you want in the operating account. The book sets it at one month of cash overhead. To size yours, see how much cash reserve a small business needs.
Show the Math
Ridgeline’s First 13-Week Forecast
Early December. $38,000 in the operating account, the best December Ridgeline Landscaping ever had. Mike’s question: will the business make it through winter without touching the line of credit?
| Week | Starting cash | Cash in | Cash out | Ending cash |
|---|---|---|---|---|
| 1 (Dec 1) | $38,000 | $56,000 | $34,900 | $59,100 |
| 2 | $59,100 | $34,000 | $29,000 | $64,100 |
| 3 | $64,100 | $19,000 | $26,000 | $57,100 |
| 4 | $57,100 | $5,000 | $6,500 | $55,600 |
| 5 (Jan 1) | $55,600 | $7,000 | $14,900 | $47,700 |
| 6 | $47,700 | $3,000 | $7,500 | $43,200 |
| 7 | $43,200 | $6,000 | $6,500 | $42,700 |
| 8 | $42,700 | $2,000 | $7,000 | $37,700 |
| 9 (Feb 1) | $37,700 | $2,000 | $20,900 | $18,800 |
| 10 | $18,800 | $2,000 | $7,000 | $13,800 |
| 11 | $13,800 | $8,000 | $6,500 | $15,300 |
| 12 | $15,300 | $10,000 | $7,000 | $18,300 |
| 13 (Mar 1) | $18,300 | $18,000 | $14,900 | $21,400 |
Fictional figures from the book. Week 9 carries a $6,000 insurance installment on top of payroll, loans, and rent.
The Method
How to Build a 13-Week Cash Forecast in 5 Steps
Start with today’s operating balance.
Week 1 is what is in the account right now. Every week after starts with the week before’s ending cash.
List cash in by when it will really arrive.
Use your aging report and how fast each customer actually pays. Collections, not sales.
List cash out in the week it leaves.
Payroll, loan payments, rent, insurance, fuel, supplies, and any tax that comes out of operating. Your loan schedule and last year’s bank statements fill most of it.
Find the lowest ending week and compare it to your floor.
Ignore the rest of the table. That one number tells you whether you are safe.
Roll it forward every Monday.
Replace last week with actuals, add a new week 13, and look at the lowest week again. Twenty minutes.
One Change and One Control
For a week below the floor, make one change that brings cash in sooner and one control that sends cash out later. Do not cut anything that shrinks next season. Ridgeline pre-sold spring cleanups with a 25% deposit, about $2,000 a week from week 7, and moved a $6,000 insurance installment to $2,000 a month. If a slow-paying customer is the problem, the deposit and the follow-up call both belong in week 1.
Before and After
What Two Small Moves Did to the Lowest Week
| Ending cash | Before | After |
|---|---|---|
| Week 7 | $42,700 | $44,700 |
| Week 8 | $37,700 | $41,700 |
| Week 9 | $18,800 | $28,800 |
| Week 10 | $13,800 | $25,800 |
| Week 11 | $15,300 | $29,300 |
| Week 12 | $18,300 | $34,300 |
| Week 13 | $21,400 | $37,400 |
Deposits add $2,000 a week from week 7. Monthly insurance keeps $4,000 in the account from week 9.
The lowest week is still week 10, now about $25,800, above the floor. In January the forecast missed by $3,100 because of an extra snowstorm, and it did not matter. Mike found out in January instead of February. The same method works for any slow season. For the bigger picture of profit vs. cash, read what is cash flow.
Owner Warning
Why Do Owners Get Surprised by Cash?
- Checking the bank balance every morning and calling it a forecast.
- Counting sales instead of collections.
- Forgetting payments that only hit once a quarter or once a year.
- Building the forecast once and never updating it.
- Reading the whole table instead of the lowest week.
- Fixing a low week by cutting what next season needs.
From the Book
Where You Are vs. Where You’re Going
Chapter 21 · Dr. Paul’s Bottom Line
The 13-Week Cash Forecast
Update it every Monday and add a week at the end. The bank balance tells you where you are. The forecast tells you where you’re going.
The full forecast, the Monday routine, a blank 13-week template, and the Ask the AI prompt for your own numbers. Get the book.
Get the Book on Amazon →Cash Tight Right Now?
For a full 90-minute crash course on cash, see Cash Flow Management for Small Businesses. If you want the forecast built with you and reviewed every month, Dr. Paul works with owners as a part-time financial lead. See fractional CFO services.
Beyond the Book
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13-Week Cash Forecast Questions
What is a 13-week cash flow forecast?
Why 13 weeks?
What should I do if the forecast shows a low week?
How often should a cash forecast be updated?
Keep Going
Related Guides
Every chapter, mapped to the page that covers it: the small business finance guide.
Written by Dr. Paul Borosky, DBA, MBA, business consultant, author, and adjunct finance instructor with an MBA focused in finance.
This page is for general educational purposes only. It is not legal, financial, tax, accounting, or lending advice. Tax rules change by place and by year. Ridgeline Landscaping and its figures are a fictional illustration from the book, not a projection for your business. For decisions about your own business, consult a qualified professional.