Property Investment Calculator

How to Use the Property Investment Calculator

A rental property has four separate returns — cash flow, principal paydown, appreciation and tax treatment — and most people judge a deal on the one they can see. This calculator builds the full annual income statement first, then reports the four ratios lenders and experienced landlords actually use.

1. Enter the price, deposit and mortgage terms. Buy-to-let and investment mortgages usually need 20% to 25% down and carry a slightly higher rate than an owner-occupier loan.
2. Add purchase costs. These matter more here than on a home, because they are part of the capital you have at risk and therefore part of the denominator in the cash-on-cash return.
3. Enter the monthly rent you can realistically achieve — the rent the last tenant paid, not the rent the listing photos suggest.
4. Set vacancy and management. A month empty a year is 8%; 5% to 8% is the normal planning range. Management runs 8% to 12% of collected rent if you do not self-manage.
5. Add maintenance, property tax and insurance. Landlord policies cost more than owner-occupier cover, and maintenance on a let property runs higher than on one you live in.
6. Read the income statement in the breakdown table. Every line is shown as a share of gross rent, which makes it obvious where the money actually goes.

The primary figure is monthly cash flow. If it is negative, the property costs you money to own every month and the whole case rests on appreciation — a bet, not an investment.

Property Investment Formulas

Four ratios, built in order. Each one answers a different question.

DSCR is the one a lender cares about. Below 1.0 the rent does not cover the mortgage; most investment lenders want 1.20 to 1.25 as a minimum, which is a margin of safety rather than an arbitrary hurdle.

Example

A $285,000 rental at $2,750 a month

1. Deposit: 285,000 × 0.25 = $71,250. Purchase costs: 285,000 × 0.03 = $8,550. Cash invested: $79,800.
2. Loan: $213,750 at 6.9% over thirty years, so the payment is $1,407.76 a month, or $16,893.09 a year.
3. Gross rent: 2,750 × 12 = $33,000. Less 6% vacancy ($1,980), effective income is $31,020.
4. Operating costs: management 31,020 × 0.08 = $2,481.60, maintenance $2,850, property tax $3,562.50, insurance $1,450. Total $10,344.10.
5. NOI: 31,020 − 10,344.10 = $20,675.90. Cap rate: 20,675.90 ÷ 285,000 = 7.25%.
6. Cash flow: 20,675.90 − 16,893.09 = $3,782.81 a year, or $315.23 a month. Cash-on-cash: 3,782.81 ÷ 79,800 = 4.74%.

Does a lender lend on it?

DSCR is 20,675.90 ÷ 16,893.09 = 1.22. That clears 1.20 but sits just under the 1.25 many investment lenders prefer, so this deal would need either a slightly larger deposit or a slightly better rent to be comfortable. Raising the deposit to 30% cuts the payment to $1,313.91 and lifts DSCR to 1.31 — the same property, a different financing structure, and a completely different underwriting conversation.

Five years out

At 3% annual growth the property is worth $330,393 after five years and the mortgage balance has fallen to $200,990, giving equity of $129,403. Against the original $71,250 deposit, that is $58,153 of equity gain, plus $18,914 of accumulated cash flow — a total gain of about $77,067. Cash flow is barely a quarter of it. That is typical, and it is why judging a rental on its monthly cash flow alone understates the return while relying on appreciation alone overstates the certainty.

Where Every Dollar of Rent Goes

Here is where every dollar of gross rent goes on the worked example.

Thirty-seven per cent of the rent never reaches you, and that is before the mortgage. New landlords routinely model 10% or 15% of costs and are then surprised when the property loses money. If your operating costs come out below 30% of gross rent, check what you have left out.

The four ratios answer four different questions, and confusing them causes most bad decisions. Cap rate tells you whether the building is priced well, independent of how you fund it. Cash-on-cash tells you what your actual money earns. DSCR tells you whether the deal survives a lender's stress test. Total gain tells you what the whole position is worth after five years.

A property can have an excellent cap rate and terrible cash flow if you borrow too much, and vice versa. Compare cap rates between properties; compare cash-on-cash against other things you could do with the same money, which is where the ROI calculator and the investment return calculator are the fairer benchmarks.

What This Model Leaves Out

What this model leaves out, and why each omission matters.

Income tax. Rental profit is taxable, and the rules on deducting mortgage interest differ sharply between countries and have changed recently in several. Depreciation allowances can turn a taxable profit into a paper loss. None of that is modelled, and all of it is worth an accountant's hour before you buy.

Capital expenditure. Maintenance covers the boiler service, not the new roof. Experienced landlords set aside a separate capital reserve of roughly 0.5% of value a year on top of maintenance. Add it to the maintenance field if you want the conservative version.

Bad tenants. Vacancy models an empty month. It does not model six months of unpaid rent, an eviction and a damaged property, which is a rare but real outcome and the single largest downside risk in small-scale letting.

Rent is not guaranteed to grow. The five-year gain figure applies price growth but holds rent flat, deliberately. If you want to model rising rent, raise the rent field and re-read the cash flow — but treat the higher number as a hope rather than a plan.

Liquidity. Selling takes months and costs 5% to 7%. A share portfolio can be sold on a Tuesday afternoon. That difference should show up as a required return premium, and on a 4.74% cash-on-cash it is fair to ask whether it does.

Before committing, check the rental yield calculator to compare this property against others on a financing-neutral basis, and the closing cost calculator to firm up the purchase costs sitting in your cash-on-cash denominator.