Folks, I tell every new investor who walks into my office in central Illinois the same thing: the money in a flip isn't made when you sell. It's made the day you buy. And the only way to buy right is to run every number on a house flipping calculator before you sign anything.
I watched a guy I mentored learn that the hard way. Years back he fell in love with a little three-bed ranch on the north side of town. Pretty street, good bones, he just knew it would sell, so he bought it on a feeling. By the time he'd carried it through a winter, fixed a furnace he never budgeted for, and paid two agents on the way out, he cleared about $4,000 on a deal he'd told his wife would make $30,000. That house taught him more than any seminar ever did, and it taught me something too: hope is not a strategy, and the numbers are sacred.
This post is the calculator I wish every new investor had before a day like that. By the end you'll be able to look at a house and know in fifteen minutes whether it's a deal or a money pit. No software required. A spreadsheet and a clear head will do.
Why You Run the Numbers Before You Make an Offer
Most folks do this backwards. They get excited about a property, decide they want it, and then go looking for numbers that justify the price. That's how you talk yourself into a bad deal.
When you run the numbers first, you flip it on its head. You start with the profit you need, and you work backward to the most you can pay. If the seller's number is under that, you might have something. If it's over, you walk. The folks I've watched build real wealth just refuse to make an offer they can't defend on paper. We don't buy houses, we solve problems, and a problem you can't measure is a problem you can't solve.
If you're still getting your head around the whole process, start with my primer on what house flipping actually is. This post assumes you already know the shape of a flip and just want to learn how to price one.
The Core Formula Behind Every House Flipping Calculator
Strip away the fancy software and every house flipping calculator runs the same five-part subtraction:
Profit = After Repair Value − Renovation Costs − Purchase Price − Holding Costs − Selling Costs
Five numbers. Get them all close to right and your profit estimate means something. Get one badly wrong, usually the first two, and the rest is fiction. Let's walk them one at a time, the way I'd walk a property with you.
Step 1 — Nail the After Repair Value (ARV)
ARV is what the house is worth after you've finished it and it's move-in ready. Not what it's worth today, and not what the seller wishes it were worth. It's what the market will actually pay for the finished product.
You find it with comps, which is just shorthand for comparable sales. Pull the homes that sold in the last 90 days, same neighborhood, same rough square footage, same bed-and-bath count, same updated condition. Here in Illinois that means I'm not comparing a flip on the east side of Bloomington to one in a different school district three miles off, even if the houses look like twins. Different district, different buyer pool, different price.
In my market a clean, fully renovated three-bedroom in a starter neighborhood runs around $185,000 to $215,000 depending on the street. That $30,000 spread is exactly why you tighten your comps. Lazy comps are how a $30,000 profit becomes a $4,000 one.
If you're brand new, don't trust your gut yet. Lean on a local agent who closes deals in your zip code, or buy through a wholesaler who's already done the comp work. Be most careful here, because every other number bends to this one.
Step 2 — Build an Honest Renovation Budget
This is where new folks get burned, every single time. People underestimate rehab. That mentee did it on his first ranch and I've watched a hundred people do it since. Walk it and price the work in buckets:
- Cosmetics: paint, flooring, fixtures, landscaping. The cheap, visible stuff.
- Big systems: roof, furnace, central air, plumbing, electrical. The expensive surprises that don't show up until you're in the walls.
- Kitchen and baths: usually your best return per dollar, also the most variable.
- A contingency: add 10 to 15 percent to whatever you came up with, because something always shows up.
In my Illinois market a light cosmetic refresh runs about $20 a square foot. A full gut, new kitchen, new systems, the works, runs $55 to $75 a square foot. So a 1,200-square-foot ranch that needs a moderate rehab is a $35,000 to $45,000 job before contingency, not the $20,000 the seller's brother-in-law swore it would be.
I'm the cheapest guy you'll ever meet, and even I walk every deal with two contractors before I lock a number, because my eyes aren't an estimate.
Step 3 — Count the Real Cost of Buying
The purchase price is obvious. The costs around it are the ones new folks forget. When you buy, plan for:
- Closing costs on the buy side: title, escrow, attorney, recording. Figure 2 to 3 percent of the purchase price in Illinois.
- An inspection.
- An assignment fee if you're buying from a wholesaler.
On a $120,000 purchase that's roughly $3,000 you'd have skipped right past if you only wrote down the sticker price. It's not a fortune, but a flip lives and dies in the margins.
How you finance the buy shapes this line too. Cash, hard money, a private lender, each changes your math. If you haven't sorted that out, start with my guide on how to finance your first house flip.
Step 4 — Add Up Your Holding Costs
From the day you close to the day you sell, the clock is running. Folks forget this one because it's invisible. It never shows up at a closing table; it just bleeds out a little at a time. Your monthly carry is:
- Loan interest. Hard money in my area runs roughly 10 to 12 percent annualized, plus points up front.
- Property taxes, prorated. Illinois taxes are no joke; on a flip they can run two or three hundred a month on a modest house.
- Vacant-property insurance, utilities while you renovate, and any HOA dues.
A typical rehab here runs four to six months from purchase to resale once you count permits, the work, and time on market. On a mid-sized deal I budget $1,500 to $2,500 a month in carry. Across five months that's $7,500 to $12,500 gone before you sell a thing. Leave it off and you'll think a deal works when it doesn't.
Step 5 — Don't Forget What It Costs to Sell
Costs come out on the way out, too, and they're bigger than people expect:
- Agent commissions, usually 5 to 6 percent of the sale price.
- Seller-side closing costs: title, transfer taxes, the rest. Another 1 to 2 percent.
- Any concessions you give up in the negotiation, plus staging if it isn't already in your rehab number.
All in, selling commonly eats 7 to 9 percent of your ARV. On a $200,000 sale that's $14,000 to $18,000 off the top, the difference between a good flip and a flat one.
The 70% Rule: A Quick Filter Before the Full Math
Before I run the full five-part calculation, I use the 70% rule to decide whether a property even deserves the deeper look:
Maximum Offer = (ARV × 70%) − Renovation Costs
Take that $200,000 ARV ranch needing $40,000 in work. Seventy percent of $200,000 is $140,000, minus the $40,000 rehab leaves a max offer of $100,000. If the seller wants $130,000, I'm out, and I knew it in thirty seconds.
Now, the 70% rule is a heuristic, not a law. Tight markets run at 75 percent or higher because margins are thinner; looser markets give you more room. But for a new investor still building a feel for deals, it's a solid first gate that keeps you from wasting a Saturday on a property that was never going to pencil. It's also the backbone of how I decide whether a project is worth taking on at all, which I cover in getting started with house flipping.
What Your Calculator Should Actually Contain
You don't need expensive software for this. A clean spreadsheet beats a fancy app you don't understand. I'm sixty years old and I still run most of my deals on a sheet I built years ago. It carries one row for each of the five numbers above plus the financing details (loan amount, rate, points, term), then spits out total cost, estimated profit, profit margin, and return on the cash you put in.
The one habit I'd add: run three versions. Best case, base case, worst case. Stretch your rehab number up and your ARV down at the same time and see if the deal still survives. If it only works in the best case, it doesn't work. If you want to graduate from a spreadsheet later, here are the apps and tools I actually use as a house flipper, but master the math by hand first.
The Mistakes I See Most Often
Even with a good calculator in front of them, here's where I watch newer folks go wrong:
- Using the asking price as the ARV. It's what the market pays for the finished house, not what the seller hopes to get.
- Skipping the contingency and the holding costs. Both feel optional. Both will eat your margin if you leave them out.
- Stretching the comps. A house that sold across the district line is not your comp, no matter how similar it looks.
Let the Numbers Make the Decision
Here's what twenty-plus years has shown me. The investors who run disciplined numbers make more money than the ones who trust their gut. Not because the calculator is magic, but because it forces you to look every cost in the eye before you commit a dime.
When you get the math right, something settles in you. You stop agonizing over every offer. You know the number that works, you write it down, and you hold to it. If the seller won't meet you there, you walk easy, because the data already told you the deal doesn't work. That's not stubbornness. That's being a good steward of what you've got.
And remember, no for now is not no forever. The seller who turns down your honest number in May sometimes calls back in August when the house hasn't moved. Run the numbers, make the right offer, and let the deal tell you what it's worth. Once the property's yours, the discipline doesn't stop, it just shifts into the build, and I walk through that in managing a house flip from start to finish.
That's how real investors build a track record, folks. One well-analyzed deal at a time.
Chris Albin and CRARE Instruction do not guarantee any level of money, success, or lifestyle from learning any of the strategies discussed here. The information in this post is of a general nature and is not intended to replace specific advice you may receive from a licensed professional for legal, financial, or business decisions. Individual results will vary depending on several factors, including your starting point, your effort, and your resources. All information is believed to be true and accurate, and is subject to change without notice.
