How to Estimate Rehab Costs per Square Foot (Light, Medium, Heavy)

A rehab cost per square foot sizes a renovation before the walk-through: square footage × a $/sq ft rate for the level of work — light, medium or heavy. As a starter range (an example, not market data), light is $10–25 per sq ft, medium $25–45, heavy $45–80; a 1,600 sq ft medium rehab lands at $40,000–72,000. It is a first filter; the real estimate is built zone by zone.

What a rehab cost per square foot can and cannot tell you

A square-foot rate answers one question well: is this house a $20,000 project or an $80,000 one? That is enough to decide whether to drive out, whether the asking price is in the right universe, and which maximum offer to sketch on the listing page.

It answers nothing else. A square-foot rate does not know whether the roof has five years left or none, whether the panel is a 100-amp Federal Pacific, whether the sewer line is clay, or whether the kitchen is a refresh or a tear-out. Two houses of the same size and the same level can differ by $20,000 on those four items alone. The rate is a filter; the walk-through is the estimate.

Rehab cost (rough) = Square feet × $/sq ft for the level
Shown as Low – Base – High, rounded to the nearest $1,000

The three levels: light, medium and heavy

The free Rehab cost by size calculator in Flip Investor OS uses three levels with a low, base and high rate for each. The figures below are the app's starter rates, labelled "Starter estimate — not market data" everywhere they appear; they are a placeholder until you load your own rates, and your market, labor costs and finish level can put you outside them.

The jump between levels is bigger than the spread inside a level. That is the practical lesson: getting the level right matters more than fine-tuning the rate.

Worked example: a 1,600 sq ft house at each level

The example house used across this site is 1,600 sq ft, 3 bed 2 bath, built in 1978. At the starter rates:

The calculator rounds each figure to the nearest $1,000, which is why the light base shows as $29,000: a rough number should look rough.

This house is a 1978 build with its original kitchen and baths, a tired but sound roof and a working furnace — a textbook medium. The square-foot screen says $40,000–72,000. The zone-by-zone estimate from the walk-through came to $48,000, or $30 per sq ft: inside the band, towards the low end, because the roof and HVAC were repairs rather than replacements. The screen did its job — it put the house in the right universe — and the walk-through did the rest.

You can open the free calculator with any square footage and level; in a property, the same levels seed a rough figure that the line-by-line estimate then replaces.

What moves a house from one level to the next

The level is decided by a short list of expensive, hard-to-see items, not by the finishes:

• Kitchen. Refresh (paint, counters, hardware) keeps a house light. A full tear-out with new cabinets, counters, appliances and possibly a moved wall is the signature of medium.
• Baths. Fixtures and a vanity are light; tile, tub, plumbing in the wall and a second bath rebuilt are medium.
• Roof. Repairs keep the level. A full replacement on its own adds a five-figure line and pushes a light house towards medium, a medium house towards heavy.
• HVAC. A service call is light; a new furnace and condenser is a medium-to-heavy item.
• Electrical and plumbing. A panel upgrade, a rewire, a repipe or a sewer line are the lines that make a rehab heavy, because they open walls and trigger permits and inspections.
• Foundation and structure. Any structural repair is heavy territory, with engineering and permits on top.
• Windows and doors. A few replacements are medium; every window in the house is heavy money.
• Layout and additions. Moving walls, adding a bath, finishing a basement or building out square footage move a house to heavy regardless of condition.

One big item can push a house up a level. A cosmetically fine house that needs a new roof, a panel and a sewer line is not a light rehab with three extras; it is a medium rehab with cosmetics on top. The walk-through checklist goes through each zone with the questions that find these items.

Why a $/sq ft figure is only a first filter

The rate hides variance in four places, and each one is money:

1. The level is a judgment. Medium on a 1978 ranch means something different from medium on a 1920s two-storey with knob-and-tube wiring. The rate cannot see the house.
2. Big-ticket items are lumpy. A roof costs what a roof costs, whether the house is 1,200 or 2,000 sq ft. Square-foot rates spread lumpy costs evenly and are wrong at both ends: too low on a small house that needs everything, too high on a large house that needs little.
3. The costs around the work are not per square foot. Permits, dumpsters, a portable toilet, utilities during the work, the contractor's overhead and profit, and a contingency for what the walls hide — none scale with floor area, and all belong in the estimate.
4. Markets differ. Labor is the largest part of most lines and varies by region, by season and by how busy the trades are. A published rate from another state is a story about that state.

That is why the square-foot number should set expectations, not the offer. The offer moves dollar for dollar with the rehab, so a $10,000 error here is a $10,000 overpayment on closing day. For the full list of what a flip costs beyond the rehab — closing, holding, financing, selling — see how much it costs to flip a house.

How a zone-by-zone estimate replaces it

The estimate that belongs in an offer is a list of lines, each with a quantity and a unit price, grouped by where the work is. Flip Investor OS walks the house in 12 zones on a phone — exterior, roof, foundation, kitchen, baths, electrical, plumbing, HVAC, interior, windows and doors, garage, yard — with photos and notes per zone, offline if the house has no signal, syncing later.

The estimate is then built from those zones:

• Each line is priced from your own rates ("My rates") when you have them, or from the starter rates until you do — and every starter-priced line carries the label "Starter estimate — not market data", so you always know which numbers are yours and which are placeholders.
• Photos help find lines, not price them. Field AI describes what is visible in a zone's photos, what is possible and what cannot be verified from a photo (a sewer line, the inside of a wall). It never prices anything; nothing enters the estimate until you confirm it. The price always comes from a rate, a bid or you.
• A contractor's bid can be read against the estimate — line by line, what the bid covers, what it leaves out, where it differs — so the number that goes into the deal is one you have compared, not one you have accepted. How to read a contractor bid covers what a good bid spells out.

The result is a low, base and high total for the whole rehab, and a list of which lines carry each part of the uncertainty. On the example house that is $48,000 in the base case; the square-foot screen said $56,000 at the medium base rate and the walk-through found a house slightly better than its age.

Unpriced, not $0

One rule matters more than any rate: an unknown cost is not zero.

When a line has no price yet — the sewer scope has not come back, the roofer has not quoted, the foundation needs an engineer — the temptation is to type $0 and move on. The total looks finished. It is not; it is wrong by the size of that line, in the direction that makes you overpay.

In Flip Investor OS an unknown line is marked Unpriced, the estimate total shows as Incomplete, and the deal analysis says what is still missing instead of showing a maximum offer built on a hole. A line gets a price when you give it one, from your rates, a bid or a supplier — and only then does the offer move.

Costs vary by market; rules of thumb are rules of thumb; a square-foot rate is where the estimate starts, not where it ends. The house tells you the rest, one zone at a time.