How to calculate ARV — and why the appraiser gets the last word
ARV — after-repair value — is what the property will be worth once the renovation is done. If you flip, ARV sets your maximum offer. If you BRRRR, ARV sets the size of your refinance, which sets how much of your cash comes back out of the deal. Get it right and the strategy works as advertised. Get it 10% wrong and the error flows through every number downstream — offer, loan, cash left in, cash-on-cash return — with nothing to stop it.
So this post takes ARV seriously as a calculation. Not the one-line version you'll see everywhere, but the way it actually gets computed — by you before the offer, and by a lender's appraiser after the rehab, whose number is the one that counts.
The formula you'll see everywhere (and what's wrong with it)
Most guides open with this:
ARV = current value + value added by renovations
It looks like arithmetic, but neither term is a number you can look up. "Current value" of a distressed house is itself an estimate, and "value added by renovations" is the entire question restated — a $40,000 rehab does not add $40,000 of value. Sometimes it adds $60,000; in an over-improved house on the wrong street, it adds $15,000. Cost is not value. The formula is circular, which is why two investors can "calculate" ARVs $30,000 apart on the same house and both show you their math.
The real definition is empirical: ARV is what renovated, comparable houses near yours have recently sold for. You don't derive it — you go find it. That's the comp method, and it's the same method the appraiser will use later, so you might as well run it their way from the start.
How to calculate ARV in five steps
1. Pull sold comps, not listings
Asking prices are opinions; closed sales are evidence. Work from properties that actually sold, as recently as you can — the last 3–6 months if the market gives you enough of them. This isn't just good practice, it's the lender standard: Fannie Mae's appraisal guidelines require at least three closed comparable sales, generally from within the last 12 months. Your ARV will eventually be graded against a number built exactly that way.
2. Match the location tightly
Stay inside the same neighborhood — ideally within half a mile, and never across a boundary the market prices: a school-district line, a highway, the street where the housing stock changes era. A comp 0.4 miles away on the wrong side of the boulevard can be worth 20% less than one two blocks from the subject. If a local agent would wince at the comparison, the appraiser will too.
3. Match the finished product, not the current one
This is the step people miss. You're valuing the house after the rehab, so your comps must be houses in after-rehab condition — renovated kitchens, updated systems, the finish level you're actually building to. Same property type, similar age and style, bedroom and bathroom count as close as you can get, and square footage within roughly ±20%. Comping your future renovated 3/2 against tired originals tells you what the house is worth if you do nothing.
4. Put them on a grid and let price-per-square-foot do the work
Say the subject is a 3-bed / 2-bath, 1,400 sq ft house, renovated to neighborhood standard. Three renovated solds nearby:
| Comp | Sold price | Sq ft | $/sq ft |
|---|---|---|---|
| A — 3/2, renovated, 0.3 mi | $209,000 | 1,450 | $144.14 |
| B — 3/2, renovated, 0.4 mi | $199,500 | 1,380 | $144.57 |
| C — 3/2, renovated, 0.5 mi | $192,000 | 1,310 | $146.56 |
Average: $145.09 per square foot. Applied to the subject's 1,400 sq ft: 1,400 × $145.09 ≈ $203,000.
Then adjust for the big, concrete differences — a garage the subject lacks, a third bathroom a comp has, a main road versus a quiet street. Adjust the comp's price toward what it would have sold for as your house's twin, re-run the average, and keep adjustments few and defensible. If a comp needs five adjustments to fit, it isn't a comp.
One warning on $/sq ft: it drifts upward as houses get smaller (the lot, kitchen, and roof are spread over fewer feet). Comping a 1,000 sq ft house against 1,900 sq ft sales will flatter it badly. Keep sizes in a tight band and the shortcut stays honest.
5. Take a range, not a point
Those three comps support a band of roughly $198,000–$205,000, not "$203,126." State your ARV as the band, underwrite the deal at the conservative end, and gut-check the result: do renovated houses on that street actually change hands at that number? If your ARV is above every sold comp you found, you don't have an ARV — you have a hope.
Why you can't just use the Zestimate
Automated valuations are built to estimate a house as it sits, from public records and market data — they cannot see the renovation you haven't done yet, and they're weakest on exactly the houses BRRRR investors buy. Zillow's own published accuracy data puts the Zestimate's median error around 2% for homes actively on the market — but around 7% for off-market homes, which is what a distressed acquisition is. And median means half the misses are bigger than that. On a $200,000 ARV, 7% is $14,000 — enough to flip the deal's verdict on its own, before the rehab budget says a word.
AVMs are useful for finding candidate comps fast and spotting when your estimate has left the atmosphere. As the number you borrow against? No.
The appraiser gets the last word
Your ARV meets reality twice, and both times someone else is holding the pen.
If you flip: the classic 70% rule sets the maximum offer as ARV × 70% − repair costs. At a $200,000 ARV with $35,000 of repairs, that's $140,000 − $35,000 = $105,000. Notice the leverage: every dollar of ARV you're wrong about moves your maximum offer by 70 cents. A 7% ARV miss is a ~$9,800 offer error on this one house.
If you BRRRR: the refinance lender orders an appraisal and lends a percentage of that number — typically 70–75% of appraised value, as covered in BRRRR basics. Run the miss:
| You underwrote | Appraisal came in | |
|---|---|---|
| Value | $200,000 | $185,000 |
| Refi loan at 75% LTV | $150,000 | $138,750 |
A 7.5% appraisal miss — right at the published median error for off-market AVM guesses, and entirely ordinary in the real world — just shrank your cash-out by $11,250. That money isn't lost; it's buried: cash left in the deal that was supposed to fund the next one. The "repeat" in BRRRR runs on ARV being right.
Protecting the deal before you offer
You can't control the appraisal, but you can decide in advance how much appraisal risk the deal survives. Underwrite at the low end of your comp band, then ask one more question: what does this deal look like if the appraisal comes in at 90–92% of my number? If the answer is "still acceptable — less cash back, but the property cash-flows and I can live with what's left in," you have a resilient deal. If the answer is "the whole thesis collapses," you don't have a deal — you have a bet on an appraiser's mood. And keep the rehab scope matched to what the comps actually reward: the market that gave you your ARV was pricing a specific finish level, not the nicest house on the block.
Where BuyBox fits — and where it doesn't
Plainly: BuyBox does not calculate ARV for you. There's no AVM inside it and no comp-puller — after-repair value comes from the work above, and pretending software can skip that work is how deals end up with hope where the ARV should be. What BuyBox does is everything downstream of the number: enter your ARV and a Deep Dive models the whole BRRRR sequence — refinance size at your lender's LTV, cash back at refi, cash left in the deal, post-refi cash flow and cash-on-cash — with every figure computed by one engine, audited against industry-standard real-estate math, and every number showing its formula when you hover it. If you just want the refinance arithmetic first, the free BRRRR calculator runs the same engine with no signup.
Because a re-run takes seconds, the stress test stops being a spreadsheet chore: run the deal at $205,000, then at $198,000, then at the appraisal-misses-by-7% number, and watch which verdicts survive. That question — which ARV does this deal need? — is worth more than any point estimate.
Frequently asked
Is ARV the same as the appraised value?
No. ARV is your pre-purchase estimate of post-renovation value; the appraised value is a licensed appraiser's opinion, built from closed comps, after the work is done. The lender uses theirs. Your job is to estimate it the way they'll compute it, then leave margin for the difference.
What if I can't find renovated comps?
Treat that as a finding, not an inconvenience. If nothing renovated has sold nearby in the last year, the market is telling you it hasn't priced the product you're planning to build — so your renovation premium is speculative. Widen the time window before you widen the map, and if the comps still aren't there, underwrite as if the premium is small. Sometimes the honest ARV answer is "this neighborhood doesn't pay for granite."
How many comps do I need?
Three solid ones beat eight loose ones — three closed, comparable sales is also the minimum a lender's appraiser must report under Fannie Mae's guidelines. If your three require heavy adjustments, keep hunting.