You’ve probably heard the line: “I run the numbers in my head.”

And while instinct is valuable, it’s also the reason flippers lose money.

Smart investors don’t guess. They model, compare, and stress-test every deal, every time.

That’s why the best flippers keep a few go-to calculators bookmarked and ready.
Because when the margins are tight (and they usually are), you need tools that do more than quick napkin math.

This article covers:

• The three calculators every flipper should use

• What each one is best at

• How to use them to avoid bad deals

• And real-world scenarios where they save your margin

Calculator #1: Maximum Allowable Offer (MAO)

What it does:

Tells you the highest you can offer on a property while still making your target profit, based on ARV and estimated rehab.

This is the first filter you should run every potential flip through.

The Basic MAO Formula

MAO = (ARV × 0.70) − Estimated Repairs

The 70% rule is just a starting point, but every MAO calculator lets you adjust that percentage based on:

• Market risk

• Competition level

• Flip timeline

• Your profit target

Why MAO Is Essential

MAO forces you to start from the resale value and work backward, instead of basing your offer on the seller’s ask or what others are bidding.

If you’re walking into a deal without a hard MAO, you’re guessing at your profit, and that’s dangerous.

What the Best MAO Calculators Include

• Adjustable ARV % thresholds (not fixed at 70%)

• Input fields for holding costs and closing costs

• A “profit target” field, so you can set your required margin

• Side-by-side MAOs for different strategies (e.g., flip vs. wholetail)

Use Cases

• You’re analyzing five potential leads and want to rank them by profit margin

• A seller counters your offer, you need to double-check how far you can push up

• Your rehab scope grows, and you need to see how that impacts your maximum allowable purchase price

Our Favorite MAO Calculators (Bookmark These)

• DealCheck.io – Fast, flexible, and includes MAO with adjustable margins

• BiggerPockets MAO Calculator – Great for beginners

• RehabValuator.com – Powerful analysis for multi-strategy deals

Calculator #2: Rehab Cost Estimator

What it does: Estimates the full rehab cost of a flip based on property type, square footage, finish level, and repair categories.

This is where flippers often lose thousands by underestimating repairs.

Why a Calculator Beats a Gut Estimate

Even experienced flippers fall into the trap of thinking:

“This looks like a $40K rehab.”

But unless you’ve built it out line by line, including:

• Demo

• Framing

• MEP systems

• Flooring

• Windows

• Cabinets

• Exterior

• Contingencies

…you’re flying blind.

What the Best Rehab Calculators Include

• Room-by-room breakdowns

• Cost-per-square-foot models (by region)

• Toggle for finish level (rental-grade, mid-level, high-end)

• Optional contingency % (you should always include 10–15%)

• Labor + materials split

• Time-based price adjustments (for inflation or regional spikes)

Use Cases

• You’re deciding whether to go light or full-gut on a potential flip

• You want to compare two finish levels (e.g., laminate vs. hardwood)

• You’re bidding out to contractors and want a baseline to challenge inflated bids

• You need to plug rehab cost into your MAO or profit calculators

Hidden Value: Scoping Budget Ranges

A great rehab calculator doesn’t just spit out one number, it gives you a range.

For example:

• Basic rehab: $38,000

• Mid-tier: $54,000

• High-end: $72,000

This lets you plan around what the neighborhood will support, and adjust your budget based on exit strategy.

Our Favorite Rehab Calculators (Bookmark These)

• FlipperForce Estimator Tool – Itemized, visual, great for beginners and pros

• HouseFlippingSpreadsheet.com – Massive template with auto-calculations

• Homewyse.com – National cost database (great for localized estimates)

Calculator #3: Flip Profit & Return Analyzer

What it does: Shows you your total return, including net profit, return on investment (ROI), and return on cash, after ALL costs are accounted for.

This is the calculator that separates flippers from hobbyists.

Why This Calculator Is a Must

Too many flippers think:

“If I buy at $200K, spend $60K, and sell at $350K, I make $90K.”

Wrong.

You forgot:

• Agent commissions (5–6%)

• Title and escrow fees

• Property taxes

• Insurance

• Loan interest

• Utilities

• Misc. carry costs

Your actual profit might be $45K, or less.

A full profit calculator helps you:

• Spot weak deals before it’s too late

• Compare flips across markets or deal types

• Adjust for real holding timelines

What the Best Profit Calculators Include

• Line-item fields for every known and hidden cost

• Input for hold time and interest rate (if financing)

• Realtor fees and buyer closing costs

• Option to model multiple exit scenarios

• Real ROI and ROC (return on cash) calculations

Use Cases

• You want to compare ROI on a $300K flip vs. a $600K flip

• You’re bringing in a partner and need to show net margins cleanly

• You’re choosing between cash purchase vs. hard money

• You’re modeling what happens if the flip takes 8 months instead of 4

Our Favorite Flip Profit Calculators (Bookmark These)

• Flipster Deal Analyzer – Clean, quick, and visual

• DealCheck ROI Calculator – Linked to your MAO and rehab inputs

• REI/kit Flip Calculator – Designed for investors using leverage

Bonus Tool: The Stress Test Scenario Planner

This isn’t a calculator on its own, but it’s a framework you can use with all three tools.

Here’s how to run a stress test:

Scenario 1: Best Case

• ARV hits full projected value

• Rehab comes in on budget

• Flip sells in 30 days

Scenario 2: Base Case

• ARV is 95% of target

• Rehab is 10% over

• DOM is 60+ days

Scenario 3: Worst Case

• ARV is 90%

• Rehab goes 20% over

• Holding costs balloon

Model all three using your calculators.

If your worst-case scenario still makes money, you’ve got a great deal. If your base-case scenario is thin, walk.

How to Organize Your Calculator Stack

You don’t need 50 calculators. You need 3 great ones, and a way to use them fast.

Here’s how to streamline your flip analysis stack:

Bookmark each in a folder called “Flip Tools.”

You want them ready on every device.

Set up a spreadsheet with all fields.

Let calculators do the work, but keep a Google Sheet with:

• MAO

• Rehab cost

• ARV range

• Profit margin

• Return %

Use consistent assumptions.

Don’t use the 65% rule in one calc and 75% in another. Pick a conservative base and apply it across the board.

Add a ‘notes’ column with what-if observations.

(e.g., “This only works if it sells for $375K+, risky in this zip.”)

Review monthly.

Market costs change. Update your assumptions for:

• Materials

• Labor

• DOM trends

• Sale price per square foot

A Real Example: One Deal, All 3 Calculators

Scenario:
Property listed at $220K
Est. ARV: $350K
Rehab: $60K

MAO Calc:
ARV x 0.70 = $245K
Minus rehab = $185K
→ You can’t pay more than $185K

Rehab Calc:
Confirms $60K mid-range rehab is realistic
High-end version would be $80K (not worth it)

Profit Calc:
Buy at $185K
Sell at $350K
Closing, hold, and agent = $30K
Net profit = ~$75K
ROI = 31%

Stress Test:
ARV drops to $335K → profit drops to $58K
Rehab rises 10% → profit drops to $52K
Still profitable

→ Decision: Move forward and offer $180K
→ Target hold: 4 months

Don’t Let Ego Replace Math

Experienced flippers don’t rely on memory or instinct alone. They run the numbers.

Even if you’ve done 20 deals, it only takes one miscalculated budget or missed margin to wipe out your year.

So keep it simple:

Three calculators. Every deal. No shortcuts.

• MAO calculator to set your buy ceiling

• Rehab estimator to set your budget

• Profit analyzer to know your real margin

Bookmark them, use them, and you’ll flip smarter than 90% of the market.