13-Week Cash Flow Forecast: Template & Guide

You're going to hit a cash shortage in 6 weeks.

You don't know it yet. But it's coming.

In month one, revenue is great. Collections are fine. Nothing looks wrong. But you have a big vendor payment coming, payroll is going to jump 15% next month due to seasonality, and your largest customer always pays 45 days late.

In week 8, you'll suddenly realize you don't have enough cash to cover payroll and the vendor payment. You'll scramble. You'll call your lender. You'll get anxiety.

Or: you could build a 13-week cash flow forecast and see it coming 6 weeks in advance.

Here's how to do it.

Why 13 Weeks?

13 weeks is about 3 months. Why 3 months?

• Long enough to see seasonality patterns
• Short enough to be accurate (you can predict 3 months out)
• Standard for lenders (they want to see 13-week rolling forecasts)
• Matches your close cycle (monthly data, 13 weeks covers most of next quarter)

Daily forecasts are too detailed. Monthly forecasts miss intra-month cash swings. 13 weeks is the Goldilocks zone.

The Basic Structure

A 13-week cash forecast has weeks 1-13 as columns (your time axis) and rows organized by cash in and cash out:

CASH IN:
- Customer A collections
- Customer B collections
- Customer C collections
- Other collections
= Total cash in
CASH OUT:
- Payroll
- Vendor A payments
- Vendor B payments
- Rent/lease
- Utilities
- Interest/debt service
- Capital expenses
- Tax payments
- Other
= Total cash out
NET CASH FLOW = Cash in - Cash out
ENDING CASH BALANCE = Beginning balance + Net flow

Step 1: Build Your Assumptions

Before you forecast, establish assumptions for collections, payments, payroll, and fixed expenses.

AR collections. For each customer: what are their payment terms (Net 30, Net 60)? When did they order? Expected invoice amount? What's their payment history — on time, 15 days late, 45 days late? For example, Customer A invoices $100K in Week 1 on Net 30 terms but historically pays on day 32 (Week 5).

AP payments. For each vendor: what are your terms? When do invoices arrive? Are you paying on time or stretching? For example, Vendor A's $25K invoice arrives Week 1 on Net 30, so you pay in Week 5.

Payroll. Weekly or bi-weekly? Does the amount vary by season? Any bonuses coming?

Other fixed expenses. Rent ($20K on the 1st), utilities ($5K mid-month), insurance ($3K quarterly), interest ($8K on the 15th).

Step 2: Map Cash In by Week

For each customer, map when you expect to collect, then total the collections expected each week:

COLLECTIONS BY WEEK:
Week 1: $0 (invoices just sent)
Week 2: $0
Week 3: $0
Week 4: $0
Week 5: $100K (Customer A collection from Week 1 invoice)
Week 6: $155K (Customer B + Customer C collections)
... etc

Step 3: Map Cash Out by Week

For each vendor payment and expense, map when you pay, then total the payments due each week:

PAYMENTS BY WEEK:
Week 1: $80K (payroll $60K + rent $20K)
Week 2: $65K (payroll $60K + utilities $5K)
Week 3: $60K (payroll)
Week 4: $60K (payroll)
Week 5: $85K (payroll $60K + Vendor A $25K)
Week 6: $60K (payroll)
Week 7: $100K (payroll $60K + Vendor B $40K)
... etc

Step 4: Calculate Net Cash Flow

For each week, net cash flow = collections - payments:

WEEK 1: $0 - $80K = -$80K
WEEK 2: $0 - $65K = -$65K
WEEK 3: $0 - $60K = -$60K
WEEK 4: $0 - $60K = -$60K
WEEK 5: $100K - $85K = +$15K
WEEK 6: $155K - $60K = +$95K
WEEK 7: $75K - $100K = -$25K
WEEK 8: $150K - $60K = +$90K
... etc

Step 5: Calculate Ending Cash Balance

For each week, ending balance = beginning balance + net cash flow:

Starting cash: $200K
WEEK 1: $200K + (-$80K) = $120K
WEEK 2: $120K + (-$65K) = $55K
WEEK 3: $55K + (-$60K) = -$5K  <- SHORTFALL
WEEK 4: -$5K + (-$60K) = -$65K  <- BIG SHORTFALL
WEEK 5: -$65K + $15K = -$50K
WEEK 6: -$50K + $95K = $45K
WEEK 7: $45K + (-$25K) = $20K
WEEK 8: $20K + $90K = $110K
... etc

You just spotted a cash shortfall in Weeks 3-5.

Step 6: Identify Problems and Solutions

In the example above, you're running out of cash in Weeks 3-5. The root cause: collections are slow (customers paying in Weeks 5-8) but payroll is due Weeks 1-7.

Your solution options:

1. Accelerate collections (call customers, offer an early-pay discount)
2. Defer expenses (delay payments, reduce payroll if possible)
3. Get a credit facility (a line of credit to cover gaps)
4. Negotiate vendor terms (push Net 30 to Net 45)

In this case, you might call Customer A and ask them to pay by Week 4 instead of Week 5, negotiate Vendor B to Net 60 (pushing payment to Week 8), and set up a $100K line of credit as backup. With those changes, your balance stays positive.

Step 7: Update Weekly

A 13-week forecast is only valuable if you update it weekly.

Every Friday: update Weeks 1-2 with actual cash flows, refine Weeks 3-13 based on new information, and add Week 14 (rolling the window forward).

For example: Week 1 collections came in at $10K (Customer A paid partial) — update the forecast. A Week 3 collection moves to Week 6 (customer called, paying late). A new $50K invoice in Week 2 expects collection in Week 7.

Spend 15 minutes on it every Friday.

The Template

Here's a simple structure you can build in Excel or Google Sheets:

                    W1      W2      W3      W4      W5    ... W13
CASH IN:
Customer A          $0      $0      $0      $0      $100K
Customer B          $0      $0      $0      $0      $0      $150K
Customer C          $0      $0      $0      $0      $0      $75K
Total IN            $0      $0      $0      $0      $100K
CASH OUT:
Payroll             $60K    $60K    $60K    $60K    $60K
Vendor A            $0      $0      $0      $0      $25K
Vendor B            $0      $0      $0      $0      $0
Rent                $20K    $0      $0      $0      $0
Utilities           $0      $5K     $0      $0      $0
Total OUT           $80K    $65K    $60K    $60K    $85K
NET FLOW            -$80K   -$65K   -$60K   -$60K   +$15K
BEGIN BALANCE       $200K   $120K   $55K    -$5K    -$65K
END BALANCE         $120K   $55K    -$5K    -$65K   -$50K

Why This Matters

A 13-week forecast:

• ✓ Shows cash shortfalls before they happen (6 weeks advance warning)
• ✓ Lets you take action (accelerate collections, defer payments, get credit)
• ✓ Builds confidence with lenders ("we have a handle on cash")
• ✓ Reveals seasonal patterns (when you're always tight on cash)
• ✓ Guides decisions (should we hire in October or wait?)
• ✓ Prevents emergencies (no more surprise cash shortfalls)

Most manufacturing companies I work with have cash problems not because they're unprofitable, but because they don't forecast. They manage cash reactively. A 13-week forecast moves you from reactive to proactive.

Common Mistakes

Assuming collections are faster than they really are. You give Net 30 terms, but customers pay in 45 days. Update your assumptions based on actual payment history.

Forgetting lumpy expenses. Quarterly insurance, annual software licenses, bonus payouts. Map these in.

Not updating weekly. You build the forecast, then never touch it. It's only valuable if you update it weekly.

Making it too complicated. A 13-week forecast should be 10-15 lines, not 100. Focus on material items — payroll, major vendors, major customers.

Not sharing with the team. Your team doesn't know you're tight on cash in Week 7. Share the forecast and ask for help — can we defer that PO? Can we accelerate this invoice?

Using It for Decisions

Once you have a 13-week forecast, you can make better decisions:

• "Should we hire this person?" Look at the cash balance in Weeks 5-13. Surplus, yes. Shortfall, no.
• "Should we accept this big customer?" Map their invoices and terms in. Will it hurt cash flow if they always pay in 60 days but you need cash in 30?
• "Should we buy this equipment?" When is the payment due, and does your balance cover it without going negative?
• "Should we take distributions?" Only if your cash balance stays positive in all 13 weeks.

The Bottom Line

A 13-week cash flow forecast takes 2-3 hours to build the first time, then 15 minutes a week to maintain.

For that small investment, you get visibility into cash gaps 6+ weeks in advance, the ability to act before problems happen, confidence with lenders and investors, and better decisions on hiring, spending, and growth.

Most manufacturers don't have one. That's why they're always stressed about cash.

Build one. Update it weekly. Use it to make decisions. You'll never be surprised by a cash shortfall again.

Ready to build your forecast? Download our 13-Week Cash Forecast Template →