How to use the real estate portfolio calculator
Enter one row per property. The example holds four fictional rentals: a duplex, a condo, a house bought for cash and a fourplex. Replace them with your own, and add or remove rows as needed.
- Value is what the property would sell for today. An appraisal, a broker opinion or recent sales of similar properties are better guides than an automated estimate.
- Loan bal. is the current principal balance on your latest mortgage statement, not the original loan amount. Enter 0 for a property owned outright.
- Rent/mo is the rent you actually collect in a typical month. If the property is often vacant, use an average that allows for it.
- Expenses/mo covers everything except the mortgage: property tax, insurance, repairs, management, HOA dues, utilities you pay and a reserve for larger repairs.
- Mortgage/mo is principal and interest only. If your payment includes escrow for tax and insurance, take those out here and put them in expenses, or they will be counted twice.
- Price paid and Cash in are what you paid for the property and how much of your own money went into it, including closing costs and cash-funded renovations.
Choose a ranking metric to reorder the table and the chart. The flags column marks any property with negative cash flow or a debt service coverage ratio below 1.20.
How each metric is calculated
All figures are annual. For each property:
Cash flow = NOI − Mortgage × 12
Cap rate = NOI ÷ Value
Cash-on-cash = Cash flow ÷ Cash invested
DSCR = NOI ÷ (Mortgage × 12)NOI is net operating income. Rent, expenses and mortgage are the monthly amounts in each row.
LTV = Loan balance ÷ Value
Total gain = Equity − Cash investedTotal gain equals appreciation since purchase plus the principal you have repaid, minus closing costs and any other cash that did not become equity. It does not include the cash flow you have already collected.
Portfolio figures add up the dollars before dividing, so larger properties count for more: portfolio cap rate is total NOI over total value, portfolio cash-on-cash is total cash flow over total cash invested, and portfolio LTV is total debt over total value.
A worked example
The four properties are worth $1,830,000 together, with $993,000 of mortgages against them. That leaves $837,000 of equity and a portfolio LTV of 54.3%.
Between them they produce $113,400 of net operating income, a portfolio cap rate of 6.20%. After mortgage payments, $30,240 a year is left, which is 4.60% on the $657,000 invested. Equity is $180,000 more than the cash put in.
Ranked by cash-on-cash return, House C comes first at 6.46%, and Condo B comes last at -2.74%. Condo B has a cash flow of -$1,920 a year and a DSCR of 0.88×. Fourplex D is positive at $6,600 a year, but its DSCR of 1.15× leaves little room if a unit sits empty, so both are flagged.
Comparing properties: which number to trust
Each metric answers a different question, and the rankings change depending on which you choose:
| Property | Cash flow / yr | Cash-on-cash | Cap rate | DSCR | Total gain |
|---|---|---|---|---|---|
| Duplex A | $5,520 | 6.00% | 6.43% | 1.26× | $73,000 |
| Condo B | -$1,920 | -2.74% | 5.18% | 0.88× | $17,000 |
| House C | $20,040 | 6.46% | 5.49% | no loan | $55,000 |
| Fourplex D | $6,600 | 3.57% | 6.79% | 1.15× | $35,000 |
Cap rate compares the properties as buildings. Fourplex D earns the most income per dollar of value, so it would rank first for a cash buyer. Cash-on-cash compares them as investments with their current financing; House C wins because it has no mortgage payment to absorb its income. Total gain shows where wealth has been built, and Duplex A leads with $73,000. Ranking by gain puts Duplex A first, by cap rate Fourplex D.
DSCR is the safety check. It says how far rent can fall, or expenses rise, before a property stops paying its own mortgage. A DSCR of 1.0 is break-even; many lenders want 1.20 to 1.25 or more, and the flag in this calculator uses 1.20.
Where the cash flow comes from
Portfolios are often uneven. In the example, House C alone provides 66% of the total cash flow, while Condo B takes money out every month. A single property that carries the rest is a concentration risk: a long vacancy or a major repair there would hit the whole portfolio.
The second table under the calculator shows each property’s share of value, equity and cash flow. When a property’s share of cash flow is much smaller than its share of equity, that equity is earning less than it could, which is worth knowing even if the property is not losing money.
What dropping the weakest property would change
Removing Condo B from the list shows what the other three produce on their own:
| All four properties | Without Condo B | |
|---|---|---|
| Annual cash flow | $30,240 | $32,160 |
| Portfolio cash-on-cash | 4.60% | 5.48% |
| Portfolio DSCR | 1.36× | 1.48× |
| Portfolio LTV | 54.3% | 51.5% |
The comparison is only a starting point. Selling Condo B would release roughly its $87,000 of equity minus selling costs and any tax, and that money would need a new home. The fair comparison is Condo B’s total return, including principal paydown and expected appreciation, against what the freed equity could earn elsewhere.
Common mistakes when comparing properties
- Counting escrow twice. If the mortgage figure includes tax and insurance and the expenses do too, cash flow and DSCR look worse than they are.
- Leaving out reserves. Roofs, water heaters and unit turnovers are irregular but certain. Without a monthly reserve, every property looks better than it is.
- Using the original loan amount instead of today’s balance, which understates equity.
- Comparing cash-on-cash across very different loans. A property refinanced to pull cash out can show a high cash-on-cash return on a small remaining investment while carrying more risk.
What this calculator does not include
- Taxes. Depreciation, mortgage interest deductions and capital gains tax on a sale are not modeled, and they can change which property is the better investment after tax.
- Time. Cash-on-cash and cap rate are one-year snapshots. Use the real estate IRR calculator for returns over a full holding period, including the sale.
- Selling costs. Equity and total gain are on paper. Turning them into cash typically costs several percent of the sale price.
- Cash flow already collected. Total gain covers equity built up, not the rent profit you have received over the years.