The Big List of Real Estate Formulas

By on December 4, 2009

As real estate investors we’re supposed to do all sorts of calculations to make sure we’re getting a good deal. But what happens if you don’t know the real estate formulas in order to do the calculations in the first place?
Never fear as long as I am here.

Here’s my big list of real estate formulas so you too can not only see if you have a good deal but also have fun with math.

Gross Scheduled Income (GSI)
GSI = Total Monthly Rents X # Units X 12 Months

Proforma GSI
This is the max income that a property will produce based on the market rents. This is not a figure that’s ever based in reality.

Gross Operating Income (GOI)
GSI X Occupancy  = GOI

The opposite of vacancy and what we use because our glass is half full, not half empty. If you have 85% occupancy, you’ve got 15% vacancy.

Net Operating Income (NOI)
GOI – Expenses = NOI

Don’t include your debt service aka mortgage payment in the expenses.  NOI is the figure that I pay the MOST attention to when evaluating a property. How much am I gonna make?

Expense Ratio
Expense Ratio = 1 – (NOI / GSI)

This is the percentage of gross scheduled income that goes to expenses.

It’s important if you want to call bull#$*! on a seller when they claim to have a 15% expense ratio.  For deals I see, this is typically around 35-40%.

Cash Flow
Cash Flow = NOI – Debt Service

It’s important to make sure the NOI and debt service numbers are as accurate as possible here. A small change in interest rate or going from a 30 year loan to a 25 year loan will have a big impact on cash flow.

CAP Rate
Capitalization Rate
CAP Rate = NOI / Price

Basically it’s the return on investment you would make if you paid cash for the property. It’s usually expressed as a market CAP rate meaning that all props in a certain market should expect this return.

Beware of high CAP rates (15-20%) and just because it has a decent CAP rate doesn’t mean it will cash flow. Some people put a lot of faith in this ratio but I personally do not.

Gross Rents Multiplier (GRM)
Price / Monthly Rent = GRM

This is a quick way to see if you have a good deal or a crappy one. Under 100 should cash flow. Under 80 and you’ve most likely got a deal.

Return On Investment (ROI)
ROI = Annual Cash Flow/Down Payment

This is the annual return that you get from cash you put into a deal. If you put down a big down payment and after all your hard work you’re only getting a 4% return then you may want to look for another strategy or just stick to the mutual funds and relax.  If you’re doing highly leveraged deals with little cash in then good for you but this number may then be meaningless.

Debt Service Coverage Ratio (aka Debt Coverage Ratio DCR or DSCR)

DSCR = NOI/Annual Debt Service
The ability to pay mortgage from the property income

Most lenders will require a minimum of 1.20. To be safe try for 1.50. At 1.00 you’re just breaking even and at .90 you’re losing money.

Internal Rate of Return (IRR)
Ok, you’re gonna have to travel back to business finance class with me now. This ratio is the net present value of a series of future cash flows. I recommend using a financial calculator for this one.  Simply stated (even though there’s nothing simple about it – see the graphic above) it’s the required rate of return which equates the Initial Cost Outlay with the present value of series of expected cash flows. In other words IRR is the rate at which the difference between ICO and present value of cash inflows in zero.

It’s ROI on steroids, taking into effect the time value of money AND equity accumulation, appreciation, and tax shelter.

One thing to note is that a property can have a decent IRR but still have negative cash flow during the time you own it so beware.

Ok, there you have it. My big, bad list of real estate calculations. Use at your own risk. And remember to always overestimate the expenses and underestimate the income.

About Susan Lassiter-Lyons

Susan is the Amazon #1 best-selling author of Getting the Money: The Simple System for Getting Private Money for Your Real Estate Deals and founder of the award-winning real estate blog, A real estate investor since 1994, Susan has raised $26.2 million in private money and participated in more than 600 transactions as an investor, broker, lender, syndicator and advisor. Susan is a dedicated trainer and her training, seminars and coaching programs have transformed the lives and businesses of thousands of real estate investors worldwide.


  1. ARodOfIron

    December 5, 2009 at 12:37 am

    Nice reference, thanks so much. Gives me the idea of building a nice set of spreadsheets out of this info so you can input the data and get all the trickled down results.

    • Susan Lassiter-Lyons

      December 5, 2009 at 11:41 pm

      Good idea!

  2. Michelle Schoen

    December 7, 2009 at 11:49 am

    Perfect timing for this one, Susan! We’re buying our first investment property, and this really confirmed that we had made a very good choice. GRM = 55! ROI = 6.2. Thank you very much!

    • Susan Lassiter-Lyons

      December 7, 2009 at 12:18 pm

      Woo hoo! Congrats Michelle.

  3. Justin

    June 25, 2010 at 2:16 pm

    Appreciate for this one, Susan!
    Good thing that you are here and you are sharing this information with us. Wow! i have nothing to say but all positive about this site.

  4. Johnathan

    December 7, 2010 at 6:06 pm

    Hey Susan

    I’m trying to find properties in advance for franchise type businesses.

    I would like to find the formula that these types of companies look for as far as land cost? I want to find the property first and do an artist rendering of the building on the property. I will be wasting my time if they need properties at 200k and all I find is 500k any ideas?

  5. Thomas Vogel

    January 5, 2012 at 12:43 pm

    Susan, Great Thought, I was thinking of putting out there, ( asking ) the R.E. Community, to Post there thoughts-formulas for all the calculations needed for Comm. Props. etc., Maybe even more like Step by Step,thought process. It would be nice, for us in the early phases, to have that info to go by, instead of a formula here and there,from everyone who knows Real Estate. Don’t take that wrong, Susan, I, and I’m sure most any of us that are trying to understand ‘Everything Real Estate’ truely do very much appreciate all the ‘Insights’ from the very knowledgable Real Estate People. For that I Personally, want to say, Thank You Very Much, Susan, and Thanks Much, to all of you, that are out there HELPING the masses, You know who You are !!! Again, Thanks Very Very Much, for all you do. Thomas Vogel ( Investor )

    • Susan

      January 12, 2012 at 8:55 am

      The thought bank is a great idea!

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