SBA Loan Calculator: How to Model Your Business Acquisition

Most buyers make an offer before they've run the math. That's optimism, dressed up as confidence. And optimism doesn't get SBA loans approved.

Before you submit an LOI on any deal, you need to know whether the financing structure actually works. That means running the numbers: what does the monthly debt service look like, does the DSCR clear the SBA's 1.25x minimum, and how much cash are you writing a check for at closing?

The free SBA loan calculator handles this in under two minutes. This guide walks through exactly how to use it: inputs, outputs, and how to interpret what the numbers mean.

Why Model Before You Offer

The asking price on a listing tells you nothing on its own. A $2M business with $400K SDE is a very different deal than a $2M business with $600K SDE. The price is the same. The financials are not.

What matters is whether the cash flow supports the debt. That's the DSCR calculation, and it's the primary filter SBA lenders use when underwriting a business acquisition loan.

Three things the model tells you before you spend serious time on a deal:

• Whether the loan gets approved. A DSCR below 1.25x means the SBA won't fund it. Finding this out after signing an LOI wastes months of your time and the seller's.
• How much cash you need at closing. Down payment plus working capital plus closing costs. These add up quickly. Modeling them in advance prevents surprises.
• How much you'll actually keep. After debt service, what's left for you? That number is your owner cash flow, and it's the real return on your equity check.

The calculator doesn't replace working with a lender. It tells you within two minutes whether a deal is worth the next two weeks of your time.

Calculator Inputs: What Goes Where

Open the SBA calculator and you'll see a set of deal inputs. Here's what each one means and where to find the numbers.

Asking Price

The seller's listed price for the business. Enter the number as-is from the listing. You'll model different scenarios by adjusting this figure. If you're planning to negotiate the price down, you can model both the asking price and your target offer side by side.

SDE (Seller's Discretionary Earnings)

The annual cash flow available to a full-time owner-operator. This number comes from the CIM's financial section, usually stated explicitly. If it's not, it's net income plus owner's salary plus benefits plus any add-backs for non-recurring expenses.

Be careful with SDE figures that rely heavily on add-backs. Every dollar of add-back that can't be substantiated with documentation should be treated skeptically. If the broker's SDE number looks inflated, adjust it down before modeling.

Down Payment Percentage

The equity you're injecting at closing as a percentage of the purchase price. SBA standard is 10% for well-structured acquisitions. Some lenders require 15 to 20% depending on the business type, deal complexity, or borrower financial profile. Start with 10% and model upward to see how it affects DSCR.

Seller Note Percentage and Terms

The portion of the purchase price the seller is carrying as a note, also expressed as a percentage. Seller notes are common in SBA deals. 5 to 15% of the purchase price is typical. They bridge the gap between the SBA loan maximum and the purchase price, and they reduce your required equity injection.

SBA rules require seller notes to be on "standby" during the first 24 months, meaning no principal payments until the SBA loan has been active for two years. Interest-only or deferred payments during standby are the norm. After standby ends, seller notes typically run 5 to 7 years at 5 to 8% interest. Model whatever terms the seller is proposing.

SBA Loan Rate and Term

The SBA 7(a) rate is variable, tied to the Prime Rate. As of early 2026, Prime + 2.75% puts the effective rate around 10 to 10.5%. The calculator defaults to 10.5%. Standard term for business acquisition is 10 years.

You can adjust these inputs to model rate sensitivity. Useful if you're considering locking in a rate or modeling what happens if rates move 1 to 2% before closing.

Buyer Compensation

If you're replacing an owner-operator role, your salary needs to come from the SDE. This input reduces the available cash flow before calculating DSCR. If the CIM shows the owner is working 50 hours a week and taking a $120K salary that's already included in the SDE calculation, this may be zero. If the owner's compensation was added back into SDE (inflating it), you need to enter your replacement salary here.

Forgetting this is one of the most common modeling mistakes. A deal that shows a 1.6x DSCR can flip to below 1.25x once you account for the salary you need to live on.

Working Capital and Closing Costs

Working capital is the cash needed to operate between collecting receivables and paying payables. It comes out of your pocket at close, separate from the purchase price. A reasonable estimate is 1 to 3 months of revenue, depending on the business's cash conversion cycle.

Closing costs typically run 2 to 4% of the loan amount for SBA deals: origination fees, legal, appraisal, environmental review. They can be rolled into the SBA loan in some structures, which preserves cash but increases the monthly payment.

Reading the Results

After entering your inputs, the calculator produces a set of outputs. Here's how to interpret them.

DSCR and Status

The DSCR (Debt Service Coverage Ratio) is the central output. Formula: adjusted SDE ÷ total annual debt service. The status classification:

• Below 1.0x (Fail): The business can't cover its debt payments. Full stop. This deal doesn't get financed.
• 1.0 to 1.25x (Risky): Technically positive, but below the SBA minimum. Most lenders won't touch this. Walk away or renegotiate the price significantly.
• 1.25 to 1.5x (Pass): Meets the SBA minimum. Lenders will look at it, but there's no cushion. A bad quarter and you're stressed. Tight, but doable.
• 1.5 to 2.0x (Good): Comfortable. The business covers debt service with room to absorb normal variance. This is where you want to be.
• Above 2.0x (Strong): The bank will love this. Significant cash cushion. These deals are rare at reasonable multiples.

For a deeper explanation of DSCR (including how different deal structures affect it and the most common calculation mistakes), see the DSCR guide.

Monthly and Annual Payments

The calculator breaks out the SBA loan payment and the seller note payment separately, then shows the combined total. This is your debt service: the number you're committed to every month regardless of how the business performs.

Compare the monthly payment to the monthly SDE (annual SDE ÷ 12). If the payment is more than 70 to 75% of your monthly cash flow, you have almost no margin for error. Seasonal businesses, businesses with lumpy revenue, or businesses going through any kind of transition need more cushion than that.

Total Cash Required at Close

Down payment + working capital + closing costs (if not financed). This is the check you're writing. Make sure this number matches the actual capital you have available, plus a reserve. Running dry at close (or shortly after) is a common way acquisitions go sideways.

Owner Annual Cash Flow

Adjusted SDE minus total annual debt service. This is what you keep after paying the bank and the seller note, above and beyond any salary you've already accounted for in buyer compensation. It's the return on your equity injection.

Divide owner annual cash flow by total cash required at close to get your cash-on-cash return. If you put $200K in and keep $80K per year after all debt service and your salary, that's a 40% cash-on-cash return. That's worth paying attention to.

Worked Example 1: A Deal That Works

Let's run a specific deal. The listing: an HVAC service company asking $1.5M with $450K SDE. That's a 3.3x multiple, within the normal range for a stable service business.

Enter these inputs into the calculator:

• Asking price: $1,500,000
• SDE: $450,000
• Down payment: 10% ($150,000)
• Seller note: 10% ($150,000), 6% interest, 5-year term
• SBA loan: $1,200,000, 10.5% interest, 10-year term
• Buyer compensation: $80,000 (you're replacing an operator role)

The calculator produces:

• Monthly SBA payment: ~$16,280
• Monthly seller note payment: ~$2,900
• Total monthly debt service: ~$19,180
• Total annual debt service: ~$230,160
• Adjusted SDE (after $80K compensation): $370,000
• DSCR: $370,000 ÷ $230,160 = 1.61x. Good.
• Owner annual cash flow: $139,840 above salary
• Total cash at close: ~$165,000 (down payment + estimated closing costs)

This deal works. DSCR of 1.61x clears the SBA threshold with cushion. The owner earns $80K salary plus $139K in residual cash flow, roughly $219K total. Not bad for a $150K equity check.

Cash-on-cash on equity injection alone: $219K ÷ $165K = 133%. That includes salary, which you'd pay yourself anyway. Strip out the salary and look at pure cash flow: $139K ÷ $165K = 84% cash-on-cash. The borrowing math is working.

Worked Example 2: A Deal That Doesn't Work

Same structure, different business. An IT staffing company asking $2M with $400K SDE. That's a 5.0x multiple. On the high end for a small business, but some staffing companies command that with strong recurring contracts.

Enter these inputs:

• Asking price: $2,000,000
• SDE: $400,000
• Down payment: 10% ($200,000)
• Seller note: 10% ($200,000), 6% interest, 5-year term
• SBA loan: $1,600,000, 10.5% interest, 10-year term
• Buyer compensation: $90,000

The calculator produces:

• Monthly SBA payment: ~$21,700
• Monthly seller note payment: ~$3,867
• Total monthly debt service: ~$25,567
• Total annual debt service: ~$306,800
• Adjusted SDE (after $90K compensation): $310,000
• DSCR: $310,000 ÷ $306,800 = 1.01x. Risky.
• Owner annual cash flow: $3,200 above salary
• Total cash at close: ~$215,000

This deal doesn't work. A 1.01x DSCR is below the SBA's 1.25x minimum. The loan won't be approved. Even if it somehow cleared underwriting, you're left with $3,200 per year in residual cash flow above your salary. One unexpected expense wipes that out.

The business might be excellent. At 5x SDE with current rates, the math doesn't support the price. Either negotiate the price down substantially, or pass. At $1.4M (3.5x SDE), the same deal structure produces a 1.48x DSCR. Workable. That's the conversation to have with the broker.

Scenario Modeling: Changing the Variables

The calculator's real value shows up when you test assumptions across multiple scenarios, not on a single run. A few scenarios worth modeling on any deal:

How Down Payment Affects DSCR

Counterintuitively, increasing your down payment improves DSCR by reducing the SBA loan principal and therefore monthly payments. On the $1.5M deal above, raising the down payment from 10% to 15% ($75K more equity) increases DSCR from 1.61x to 1.72x. Worth knowing if a lender is pushing for more equity.

How Seller Notes Help

Seller notes reduce the SBA loan principal, which reduces monthly debt service. The seller note itself has payments, so the math isn't purely additive. On short seller note terms (5 years), the seller note payment is relatively high per dollar borrowed compared to the 10-year SBA loan. Model different seller note percentages and terms to find the structure that maximizes DSCR.

Rate Sensitivity

If rates drop 1% before closing, what does DSCR look like? If they rise 1%? This is particularly relevant for deals with 60 to 90 day SBA timelines. Rates can move meaningfully during that window. Deals that barely pass at 10.5% could fail at 11.5%.

Revenue Sensitivity

The SDE in a CIM is a snapshot of historical performance. What if revenue drops 10% post-close (a key customer leaves, a seasonal year normalizes)? Model the deal with SDE down 10 to 15% and verify it still clears 1.25x DSCR. If it doesn't, you have almost no cushion for business risk. Factor that into your offer price.

What "Good" Numbers Look Like for SBA Approval

Lenders are looking for deals that meet underwriting standards and leave some buffer. The numbers that reliably get approved:

• DSCR above 1.25x. Meets minimum. Above 1.5x is preferred. Many lenders have informal floors above 1.25x for deals they're comfortable with.
• Multiple below 4.5x SDE. Above 4.5x requires strong justification (recurring revenue, contracts, strong management). Most SBA-friendly deals price at 2.5 to 3.5x.
• Down payment at 10 to 15%. The standard range. Below 10% and lenders get nervous. Above 15% and you're overinvesting equity for the return.
• Seller note at 5 to 15%. Shows the seller has skin in the game and believes in the business. Above 20% raises questions about deal structure.
• Buyer compensation modeled realistically. If your salary needs are high relative to SDE, the deal may not pencil even if gross DSCR looks fine.

For a complete picture of how SBA lenders think about deal structure, the SBA 7(a) loan guide covers eligibility, guarantee mechanics, and the full application process.

From Calculator to Offer

Once the calculator shows you a deal that works (DSCR above 1.25x with comfortable cushion, total cash required within your available capital, owner cash flow that makes the risk worth taking), you're ready to build the LOI.

The deal structure you modeled becomes the LOI's financial framework: purchase price, down payment, seller note percentage and terms, financing contingencies (with the SBA loan as the primary contingency). The numbers you've already run are the numbers you put in the offer.

One practical step before submitting: run the same model with the SDE reduced by 10%. If the deal still clears 1.25x DSCR at lower SDE, you have a defensible cushion. If it fails, you're betting on the business performing exactly as modeled. That's a bet dressed up as an acquisition.

The model doesn't guarantee anything. It separates the deals worth pursuing from the ones that look interesting until you run the numbers. That distinction is the whole game.

Open the free SBA loan calculator and run a few scenarios on deals you're currently looking at. The math either works or it doesn't. Better to know now than after you've spent two months in due diligence.

For the full acquisition process (from defining your buy box through closing), see how to buy a small business. For DSCR deep-dives and worked examples with different deal structures, see what is DSCR.