Property Cash Flow Calculator

Property cash flow calculator computes monthly net cash flow from rental property: effective rent (after vacancy) minus all operating expenses (mortgage, taxes, insurance, maintenance, management). Positive cash flow = property pays you each month. Negative = you subsidise the property hoping for appreciation.

Example: 2,000 monthly rent, 8% vacancy, 1,200 mortgage, 150 taxes, 100 insurance, 150 maintenance, 200 management (10%). Effective rent 1,840 - total expenses 1,800 = 40 monthly cash flow. 480/year on 80k cash invested = 0.6% CoC return. Mediocre - need either rent increase or expense reduction.

The 50% rule: operating expenses (excluding mortgage) typically run ~50% of gross rent. 2,000 rent → expect ~1,000 operating expenses excluding mortgage. Mortgage payment then determines cash flow. Quick screen: gross rent × 0.5 - mortgage = approximate monthly cash flow. Useful for rapid deal evaluation before deep-diving into specific expenses.

Quick example

With monthly rent of 2,000 and monthly mortgage payment of 1,200 (plus monthly property taxes of 150 and monthly insurance of 100), the result is 40.00. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.

Which inputs matter most

You enter Monthly Rent, Monthly Mortgage Payment, Monthly Property Taxes, Monthly Insurance, and Monthly Maintenance Reserve. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.

What's happening under the hood

Effective rent (after vacancy) minus all monthly operating expenses including mortgage. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.

Why investors run this

Most people's intuition for compounding is wrong — not because the math is hard, but because linear thinking doesn't account for curves. Running numbers through a calculator like this one is the cheapest way to recalibrate that intuition before making an irreversible decision about contribution rate, asset mix, or retirement age.

What this doesn't capture

Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. The number represents one scenario rather than a forecast.