# House Flipping Guide: How to Calculate ARV, 70% Rule, and Profit Margin Underwrite house flips with professional precision. Learn how to calculate after-repair value (ARV), maximum allowable offer (MAO), repair contingency, and financing drag. --- - **Canonical URL:** https://dothecalculation.com/blog/property/house-flipping-guide - **Category:** Real Estate & Property - **Author:** Do The Calculation Team - **Published:** 2026-06-07 - **Last updated:** 2026-07-07 - **Reading time:** 16 min read - **Publisher:** Do The Calculation (https://dothecalculation.com) - **Methodology:** https://dothecalculation.com/methodology --- ## Introduction to Flip Underwriting A profitable house flip looks impressive when the final staging is complete, but the actual money is made or lost before the purchase contract is even signed. Many aspiring flippers get caught up in the cosmetic details of design and layout, neglecting the strict math required to survive. Successful flipping requires treating the acquisition as a rigorous underwriting exercise. If your purchase price, rehab budget, or carrying cost assumptions are flawed, no amount of staging can rescue your profit margin. ## Quick Takeaways - ARV (After-Repair Value) is not a guess. It must be derived from highly comparable, recently sold homes in finished condition. - The 70% Rule is a rapid screening heuristic, not a replacement for comprehensive line-item underwriting. - Total project costs must account for buying costs, selling commissions, and holding interest, not just purchase and rehab costs. - Holding costs (lender interest, property taxes, insurance, utilities) accumulate daily and eat into your margin if the timeline slips. - A renovation budget needs a healthy contingency buffer (typically 10% to 15%) to handle hidden structural or mechanical issues. ## Core Terms in House Flipping Math Before running a deal analysis, you must master the fundamental definitions used by professional real estate investors: - After-Repair Value (ARV): The estimated market value of the property once all renovations are completed to retail-market standards. - Rehab Costs: The total capital required for materials, permits, labor, and project management to complete the renovation. - Holding Costs: The carrying costs incurred during the holding period, including mortgage interest, property taxes, insurance, utilities, and HOA fees. - Maximum Allowable Offer (MAO): The maximum price you should pay to purchase the property while preserving your target profit margin. - Return on Investment (ROI): The project's net profit divided by the total project cost, expressed as a percentage. ## Why Real Estate Flipping Is a Numbers Game Flipping properties carries significant risk because you are working against a ticking clock. Hard money loans carry higher interest rates, and municipal taxes, insurance premiums, and utilities never stop accumulating. If a project takes nine months instead of six, your holding costs can erode your entire projected margin. Underwriting provides the objective metrics required to decide whether a property is a viable deal or a financial trap. It forces you to prioritize margins over emotion. _[Figure: Two Very Different Ways to Look at the Same Flip — The spread between disciplined underwriting and hopeful underwriting is usually where profits disappear.]_ ## The Formulas for House Flipping The Do The Calculation House Flipping tool uses clear, industry-standard formulas to evaluate deal feasibility: **DTC House Flipping Calculation Formulas** ``` Loan Amount = Purchase Price + Repair Costs Monthly Interest = Loan Amount × (Annual Interest Rate / 100 / 12) Total Holding Interest = Monthly Interest × Holding Period Months Total Project Cost = Purchase Price + Repair Costs + Total Holding Interest + Buying & Selling Costs Net Profit = After-Repair Value (ARV) - Total Project Cost ROI = (Net Profit / Total Project Cost) × 100 MAO (70% Rule) = (ARV × 0.70) - Repair Costs ``` - The calculator assumes that the acquisition loan covers both the purchase price and the rehab budget. - Buying and Selling Costs are entered as a total dollar amount representing closing costs, agent commissions, and title fees. ## Step-by-Step Method to Underwrite a Flip To analyze a prospective house flip, perform the following steps in sequence: - Determine the ARV: Study recent sales of fully renovated homes within a 0.5-mile radius of the property to establish a realistic exit price. - Establish the Rehab Budget: Inspect the property to compile a detailed scope of work. Price out labor and materials, then add a 10% to 15% contingency buffer. - Run the 70% Rule: Calculate the Maximum Allowable Offer (MAO) to set your absolute bidding ceiling. - Model the Financing: Input your expected interest rate and holding timeline (including renovation time and listing/closing time) to estimate the total carrying interest. - Add Buying & Selling Costs: Account for transfer taxes, escrow fees, title insurance, and listing agent commissions (usually 5% to 6% of the sale price). - Compare Net Profit and ROI: Subtract your total project cost from the ARV to verify if the final yield justifies the risk. _[Figure: A Practical Flip Underwriting Sequence — Run the deal in this order so each step is built on a number you already trust.]_ ## Worked Example Tied to Actual Calculator Logic Let's evaluate a deal using the default values from the live House Flipping Calculator: - Purchase Price: $150,000 - Estimated Rehab Costs: $40,000 - Annual Financing Interest Rate: 8% - Expected Holding Period: 6 months - Buying & Selling Costs (Closing/Commissions): $8,000 - After-Repair Value (ARV): $250,000 First, calculate the loan amount and the monthly financing interest: \[\text{Loan Amount} = \$150,000 + \$40,000 = \$190,000\] \[\text{Monthly Interest} = \$190,000 \times \frac{0.08}{12} = \$1,266.67\] Next, calculate the total carrying interest across the 6-month hold: \[\text{Total Holding Interest} = \$1,266.67 \times 6 = \$7,600\] Combine all components to calculate the total project cost: \[\text{Total Project Cost} = \$150,000 + \$40,000 + \$7,600 + \$8,000 = \$205,600\] Finally, calculate the projected profit, return on investment, and Maximum Allowable Offer (MAO): \[\text{Net Profit} = \$250,000 - \$205,600 = \$44,400\] \[\text{ROI} = \frac{\$44,400}{\$205,600} \times 100 = 21.60\%\] \[\text{MAO (70% Rule)} = (\$250,000 \times 0.70) - \$40,000 = \$135,000\] Notice that the MAO ($135,000) is lower than the actual purchase price ($150,000). This indicates that while the project is projected to yield a profit of $44,400, buying the property at $150,000 violates the 70% rule, meaning your margin of safety is narrower than typical guidelines suggest. _[Figure: Where the Example Project Cost Comes From — This makes it easier to see which pieces actually control the economics.]_ ## Performance Scenarios: ARV Sensitivity Table resale prices fluctuate based on market velocity. The table below analyzes how changes in the achieved After-Repair Value (ARV) impact your profit margins, assuming a $150,000 purchase price, $40,000 rehab, 6 months hold, and $8,000 fees: **ARV Sensitivity Table ($150,000 purchase price, $40,000 rehab, 8% interest, 6 months hold)** | Achieved ARV | Total Project Cost | Net Profit | Project ROI | MAO (70% Rule) | | --- | --- | --- | --- | --- | | $220,000 | $205,600 | $14,400 | 7.00% | $114,000 | | $250,000 (Default) | $205,600 | $44,400 | 21.60% | $135,000 | | $280,000 | $205,600 | $74,400 | 36.19% | $156,000 | ## Common Underwriting Mistakes in House Flipping - Inflating the ARV: Choosing the highest sold comp in the neighborhood rather than a realistic average, leading to overpaying for the property. - Underestimating Rehab Costs: Forgetting to account for structural repairs, electrical upgrades, permits, or ignoring a rehab contingency buffer. - Neglecting Carrying Costs: Forgetting that utility bills, lawn care, property taxes, insurance, and lender interest pile up every month the property remains unsold. - Ignoring Transaction Costs: Failing to model buying closing fees and final resale broker commissions (which typically swallow 5% to 6% of the sales price). ## Limitations of the Calculator and Underwriting Assumptions While the Do The Calculation House Flipping tool is a powerful screening asset, investors should note its built-in constraints: - Financing Assumption: The calculator models holding costs solely through the monthly loan interest on a loan that funds 100% of the purchase and repairs. If you use cash for repairs or pay points upfront, your capital structure will differ. - Simplified carrying costs: Operating carrying costs (property taxes, utilities, insurance) are not itemized separately; they must be manually estimated and added to the buying/selling cost field if you want a complete cash flow model. - Static Hold Period: The model assumes a fixed project duration. In reality, permit delays, contractor delays, or slow resale times can cause the hold period to stretch dynamically, compounding carrying costs. ## Trust & Disclaimer Section > **Important Financial Disclaimer** — This guide and the corresponding house flipping calculator are for educational and planning purposes only. Real estate flipping involves substantial risk, including contractor performance issues, hidden structural damage, permitting delays, and macro market changes. Always perform a physical home inspection, obtain verified general contractor bids, research local building ordinances, and consult with certified financial, tax, and legal professionals before buying real estate. ## Sources to Verify or Cite - Local Multiple Listing Service (MLS) or county property records for verified comparable sales and price history. - Lender term sheets for current hard money or commercial lending rates, fees, and points structures. - Local municipal building departments for building permit timelines, fee schedules, and resale compliance requirements. ## How to Use the House Flipping Calculator To test a prospective deal, navigate to the interactive calculator on our site. Input the purchase price, ARV, rehab estimate, and financing terms to instantly determine your project profit, ROI, and Maximum Allowable Offer (MAO). Tool: [Open the House Flipping Calculator](https://dothecalculation.com/calculators/house-flipping-calculator) — Input acquisition details, renovation estimates, and loan rates to calculate profit margin, project ROI, and maximum allowable offer (MAO). ## Related Resources - Analyzing Business Valuations & Exit Metrics — Learn how maximum allowable offers (MAO) and repair budgets impact your business margins. - Down Payment Savings Plan — Plan your capital collection timeline to ensure you have sufficient reserves for down payments, rehab margins, and cash reserves. ## Frequently Asked Questions **What is ARV in house flipping?** ARV stands for After-Repair Value. It is the estimated market value of the property once all renovations are completed to retail-market standards, based on comparable property sales. **What is the 70% rule in house flipping?** The 70% rule states that an investor should pay no more than 70% of the property's After-Repair Value (ARV) minus the estimated repair costs. The remaining 30% acts as a buffer to cover transaction costs, holding costs, and profit margin. **Why do holding costs matter so much?** Holding costs accumulate daily. Interest payments, taxes, insurance, and utilities continue to run whether the project is on track or delayed. A delay of just a few months can eliminate your entire projected profit margin. **Should I separate repair contingency from the rehab budget?** Yes. You should build a detailed line-item rehab budget based on actual subcontractor bids, and then add a separate 10% to 20% contingency line to cover unexpected structural, plumbing, or electrical issues discovered during demolition. **What is a typical ROI on a house flip?** Many professional flippers look for a project ROI of 15% to 20%+ relative to total project costs to justify the capital, time, and stress involved in managing a rehab. ## Summary House flipping success is determined by objective underwriting. By establishing a realistic ARV, planning a comprehensive rehab budget with a contingency reserve, and modeling financing carrying costs, you can avoid thin deals and overleveraged acquisitions. Use the House Flipping Calculator to test your assumptions and secure a safe margin of safety. --- _Source: [Do The Calculation](https://dothecalculation.com/blog/property/house-flipping-guide). Quote freely with attribution and a link to this page._