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Cap Rate Calculator Explained: The One Number Every Real Estate Investor Must Know

Blog › Finance · 9 min read · Published 2026-05-05

Cap rate cuts through financing differences and tells you the true unleveraged yield of a rental property. Here's how to use it without getting tricked.

What Cap Rate Actually Measures

Cap rate (capitalization rate) is the simplest, most universal yardstick in real estate investing: it's the unleveraged annual yield a property generates on its purchase price. Two investors looking at the same building — one paying cash, one with 80% financing — will compute wildly different ROIs. But they'll see the same cap rate, which is exactly why brokers, appraisers and institutional buyers all anchor on it.

Use the Cap Rate Calculator to run any deal in 30 seconds.

The Formula, Step by Step

  1. Start with gross annual income — total potential rent at 100% occupancy.
  2. Subtract vacancy — typically 5–10% in stable markets.
  3. Subtract operating expenses — property tax, insurance, maintenance, management, utilities, capital expenditure reserve. Crucially: do not subtract mortgage payments.
  4. Divide NOI by purchase price and multiply by 100.

Example: $500,000 property, $48,000 gross rent, 5% vacancy, $12,000 opex. Effective gross = $45,600. NOI = $33,600. Cap rate = 33,600 / 500,000 = 6.72%.

What Is a Good Cap Rate?

It depends entirely on market and asset class:

  • San Francisco / NYC multifamily: 3.5–4.5% — buyers accept low yield because they expect appreciation.
  • Suburban Sun Belt apartments: 5–6.5% — solid balance of income and growth.
  • Tertiary market single-family rentals: 7–9% — higher yield, slower appreciation.
  • Mobile home parks, self-storage: 6–10% — operationally intensive but cash-flow heavy.

Cap Rate vs ROI vs Cash-on-Cash

Cap rate

NOI / price. Ignores financing. Best for comparing properties.

Cash-on-cash return

Annual cash flow / cash invested. Includes mortgage. A 6% cap rate property with 75% financing can throw off 12%+ cash-on-cash because leverage amplifies returns.

Total ROI

Adds appreciation, principal paydown and tax benefits. The "real" return — but harder to compare across deals because assumptions vary.

Using Cap Rate to Reverse-Engineer Value

Flip the formula and you can value any property: Value = NOI / Cap Rate. If you know that local 4-plexes trade at 6.5% caps and your target has $40k NOI, fair value is roughly 40,000 / 0.065 = $615k. The Cap Rate Calculator shows implied values across 4–8% so you can see how sensitive the price is.

When Cap Rate Lies

Cap rate is silent on three things that can sink an investment:

  1. Capital expenditure backlog — a "9% cap" with a $100k roof needed in two years isn't really 9%.
  2. Rent quality — high in-place rents may be unsustainable. Always run a "market rent" cap rate too.
  3. Growth trajectory — a 4% cap in a market with 5% rent growth beats a 7% cap in a market that's flat.

How to Compare Properties Like a Pro

Build a side-by-side table for every shortlist deal: cap rate, cash-on-cash, gross yield, price per unit, price per sq ft. Pair the Cap Rate Calculator with the Real Estate ROI Calculator and the Rental Yield Calculator to triangulate fair value before you write an offer.

The Bottom Line

Cap rate isn't a complete picture, but it's the fastest filter you have. Memorize the formula, know your market range, and never make an offer without computing it.

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