← Back to Home

How we calculate

Every formula is open. Every default is documented. No black box.

Rental analysis formulas

These metrics power every long-term rental analysis on Proformatic.

Net Operating Income (NOI)

Annual income from the property after all operating expenses, but before debt service (mortgage payments).

NOI = (Effective Monthly Income − Operating Expenses) × 12

Effective Monthly Income = Gross Rent + Other Income − Vacancy Loss. Operating Expenses include property tax, insurance, maintenance, management, HOA, utilities, and any custom expenses. Mortgage is excluded.

Cap Rate

Measures the property's return independent of financing. Higher is better.

Cap Rate = (NOI ÷ Purchase Price) × 100

A 7% cap rate means the property generates 7% of its value in annual net income. Typical target: 5–10% depending on market.

Cash-on-Cash Return

Annual cash flow as a percentage of the total cash you put in (down payment + closing costs).

CoC Return = (Annual Cash Flow ÷ Total Cash Invested) × 100

Total Cash Invested = Down Payment + Closing Costs. Target: 8–12%+ for a strong deal.

DSCR (Debt Service Coverage Ratio)

How many times your NOI covers your annual debt payments. Lenders typically require 1.25x or higher.

DSCR = NOI ÷ Annual Debt Service

Annual Debt Service = Monthly Mortgage × 12. A DSCR of 1.0 means you exactly break even. Below 1.0 means the property doesn't cover its debt.

GRM (Gross Rent Multiplier)

Quick ratio to compare properties. Lower is better — it means you're paying fewer years of rent for the property.

GRM = Purchase Price ÷ Annual Gross Rent

Expense Ratio

Percentage of effective income consumed by operating expenses. Lower is better.

Expense Ratio = (Operating Expenses ÷ Effective Income) × 100

Target: under 50%. Above 80% means almost all income goes to expenses.

Monthly Cash Flow

Cash Flow = Effective Monthly Income − Operating Expenses − Mortgage Payment

This is what's left in your pocket each month after everything is paid. Target: $200+/month per unit.

5-Year IRR

Internal Rate of Return over 5 years, accounting for cash flow, appreciation, and loan paydown. Solved using the Newton-Raphson method on the NPV equation.

Find r where: ∑ CF(t) ÷ (1+r)^t = 0

CF(0) = negative total cash invested. CF(1-4) = annual cash flow. CF(5) = annual cash flow + estimated sale proceeds (appreciated value minus remaining loan balance minus selling costs).

Flip analysis formulas

Metrics for evaluating fix-and-flip profitability.

Net Profit

Net Profit = ARV − Purchase Price − Rehab Cost − Closing Costs − Holding Costs − Selling Costs

Return on Investment (ROI)

ROI = (Net Profit ÷ Total Cash Needed) × 100

Total Cash Needed = Down Payment + Closing Costs + Rehab Costs (adjusted for financing). Target: 15%+ per flip.

Profit Margin

Profit Margin = (Net Profit ÷ ARV) × 100

How much of the final sale price is pure profit. Target: 10%+.

70% Rule

Industry rule of thumb: your total investment (purchase + rehab) should be at or below 70% of the ARV to leave room for profit and unexpected costs.

Investment Ratio = (Purchase Price + Rehab Cost) ÷ ARV × 100

At or below 70% = strong. 70–85% = risky. Above 85% = very tight margins.

BRRRR analysis formulas

Buy, Rehab, Rent, Refinance, Repeat. All rental metrics apply post-refi, plus these BRRRR-specific calculations.

Cash Back at Refinance

Cash Back = New Loan Amount − Remaining Initial Loan Balance

New Loan Amount = ARV × Refi LTV%. The more equity you force through rehab, the more cash you recover.

Cash Left in Deal

Cash Left = Total Cash Invested − Cash Back at Refi

The BRRRR goal is to get this to $0 or below — meaning you recovered all your cash and can repeat the process.

Post-Refi Cash-on-Cash Return

Post-Refi CoC = Post-Refi Annual Cash Flow ÷ Cash Left in Deal × 100

If Cash Left ≤ 0, this becomes an infinite return — you have no money in the deal and it's still cash flowing.

Equity Captured

Equity Captured = ARV − New Loan Amount

Built-in equity from forced appreciation through rehab. This is your margin of safety.

Deal score algorithm

Every deal gets a composite score from 0–100, converted to a letter grade. The score is a weighted average of individual metric scores, each scaled 0–100. Here are the exact weights and thresholds.

Grade scale

ScoreGrade
95+A+
90–94A
85–89A-
80–84B+
75–79B
70–74B-
65–69C+
60–64C
55–59C-
45–54D
Below 45F

Rental deal scoring

FactorWeightScoring scale
Cash-on-Cash Return30%0% = 0 pts, 8% = ~67 pts, 12%+ = 100 pts
Cap Rate20%0% = 0 pts, 5% = 50 pts, 10%+ = 100 pts
DSCR20%<1.0x = 0–30 pts, 1.25x = ~65 pts, 1.5x+ = 100 pts
Monthly Cash Flow20%Negative = 0–20 pts, $200 = ~50 pts, $500+ = 100 pts
Expense Ratio10%80%+ = 0 pts, 50% = ~67 pts, 35% or less = 100 pts

Flip deal scoring

FactorWeightScoring scale
Return on Investment30%0% = 0 pts, 15% = 50 pts, 30%+ = 100 pts
Profit Margin25%0% = 0 pts, 10% = 50 pts, 20%+ = 100 pts
Net Profit25%Loss = 0 pts, $25K = ~55 pts, $50K+ = 100 pts
70% Rule20%70% ratio = 100 pts, 85%+ = 0 pts

BRRRR deal scoring

FactorWeightScoring scale
Post-Refi CoC Return25%Infinite return = 100 pts, 8% = ~53 pts, 15%+ = 100 pts
Cash Recovered at Refi25%$0 left in deal = 100 pts, <$5K = 90 pts, >$50K = 20 pts
Post-Refi Cash Flow20%Negative = 0–20 pts, $200 = ~50 pts, $500+ = 100 pts
DSCR15%<1.0x = 0–30 pts, 1.25x = ~65 pts, 1.5x+ = 100 pts
Equity Captured15%$0 = 10 pts, $25K = ~40 pts, $75K+ = 100 pts

Default assumptions

When you enter a purchase price, we auto-fill these starting values. Every one is overridable — they're starting points, not assumptions.

FieldDefaultRationale
Monthly rentYou enter itWe never auto-estimate rent. You know your market better than any formula. Enter actual or expected rent based on your own research or comps.
Property tax1.1% of priceUS national average. Ranges 0.3% (Hawaii) to 2.4% (New Jersey). Always verify with your county assessor.
Insurance0.5% of priceBaseline for standard coverage. Flood/hurricane zones will be higher.
Vacancy5%Approximately 18 days/year. Conservative for most markets.
Maintenance5% of rentCovers routine repairs. Older properties may need 8–10%.
Management8% of rentStandard professional management fee. Include even if self-managing — your time has value.
Down payment20%Conventional loan minimum for investment properties.
Interest rate7.0%Approximate current market rate for 30-year investment property loans.
Closing costs3%Typical buyer closing costs as percentage of purchase price.

10-year projection model

The projection chart models property performance over 10 years using adjustable growth assumptions.

AssumptionDefault
Annual rent growth3%
First-year rent growth0%
Annual expense growth3%
Annual property appreciation2%

Year N property value = Purchase Price × (1 + Appreciation)^N. Rent compounds similarly. Loan balance follows standard amortization. All assumptions are editable in the projection chart.

Try the formulas yourself

Every formula above powers our free calculators. No account required.

Ready to run the numbers?

Every formula above runs in real time as you type. No spreadsheet required.

Start your free trial