Ask HN: How does one size a market?

There's probably a lot of truth to that, but there are sources of information... you may just have to do some digging. For starters, the big analyst firms (Gartner Group, Forrester, IDC, etc.), do a lot of research on this stuff and publish reports and whitepapers that you can use. They do publish some information for free, but a lot of it is kinda pricey. You can also commission custom research / studies to answer specific questions. The problem is - as you might guess - this stuff isn't necessarily cheap.

Outside of those guys, there is market research you can do using information from the US Census Bureau, various State government agencies, and local / regional trade associations. You may have to extrapolate and make some guesses, but you can probably come up with something that's a little bit better than complete BFM / "pulled from thin air."

This book:

http://www.amazon.com/Successful-Business-Research-Straight-...

is fairly inexpensive and gives some useful - if basic - advice on doing preliminary market research.

Note that there are also smaller market research firms (sometimes as small as one individual) that you can hire to do custom market research. I've never used any of these outfits, so I can't really speak to how expensive or how effective they are. But I know they are out there.

You may also find some useful information by trawling through the "Market Sizing" and/or "Market Research" topics on Quora:

http://www.quora.com/Market-Sizing

http://www.quora.com/Market-Research

For your J2EE example I'd have a look at the existing products out there and see how many users they have (if it's open source look at their download figures, if it's commercial see if the company accounts are publicly available). Remember you don't need a precise figure, an order of magnitude will do for judging a market size.

For your web based staff planning application, I think you need to be much more specific about what your product does. If you can't figure out which business your product will apply to then you'll have a hard time selling to them. Start by thinking how you'll identify customer to sell to and the generalize from that.

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there are 7500 hospitals in the US which could buy my product for $100,000 dollars per hospital, but only 25% of them would actually be able to purchase it for various reasons of which I only have the ability to produce/call/sell to 10% of those in the first year == ((7500 x 100,000) x .25) x.10== ~$18,000,000 addressable market.

Then I would get even more pessemistic and assume that you'll have an exceptionally long sales cycle getting out of the gate and that you'd only land say 10% of those customers in the first 12-18 months. while not hitting your stride fro say 36 months.

Calc out your opex and this gives you an idea of the funds needed to support your runway.