FORTUNE — Human resource software company Workday WDAY last night priced the largest venture-backed IPO since Facebook FB , raising $637 million. Unlike Facebook, however, Workday has seen its shares soar more than 75% — climbing from the $28 per share offering price to nearly $50 (as of this writing).

Kind of seems that Workday FB left some big money on the table. Possibly more than half a billion dollars. Maybe the Morgan Stanley bankers were still feeling some Facebook shell-shock. We’ll return to this in a few months, once we see where Workday stock settles out.

In the meantime, let’s take a look at how the venture capital backers are making out. At least in terms of holding values, since it does not appear that any insiders sold shares via the IPO.

Workday doesn’t detail how many shares each firm acquired in each of the company’s five rounds of private financing, but we do at least have some basic parameters. It also does

  • Series A (2005): $15 million raised at $0.50 per convertible preferred share
    Investors: Greylock Partners
  • Series B (2006): $20.25 million raised at $1.25 per convertible preferred share
    Investors: Greylock Partners
  • Series C: (2008) $28.46 million raised at $2.50 per convertible preferred share
    Investors: Greylock Partners
  • Series D (2008): $30 million raised at $3.00 per convertible preferred share
    Investors: Greylock Partners
  • Series E (2009): $75.75 million raised at $3.30 per convertible preferred share
    Investors: New Enterprise Associates, IndoUS Venture Partners, Greylock Partners
  • Series F (2011): 7.55 million shares at $13.26 per share
    $100 million
    T. Rowe Price, Morgan Stanley Investment Management, Janus Capital Group and Bezos Expedition

We know from the offering documents that Greylock currently holds around 15 million Class B shares and NEA holds just under 14 million Class B shares. Let’s assume that Greylock took 95% of those Series A-D rounds (with individuals like Dave Duffield doing the remainder), while NEA took around 61% of the Series E round (with Greylock taking another 7.5%). Yes, these are largely guesses, but should give us a ballpark. At that point, Greylock invested around $82 million for a position valued today at more than $744 million (using $49 per share).

For New Enterprise Associates, we know that it invested $46 million for a position now valued at around $683 million.

As for the four firms in the Series F financing, let’s assume they split the investment evenly at $25 million each. Those stakes would now be valued at around $92 million.

Again, all of this is paper value until the lockups expire. But, for now, these firms and their investors are looking at returns that range from 3.7x up to nearly 15x. Not bad for an enterprise software play that spent the past few years being overshadowed by the likes of Groupon GRPN and Zynga ZNGA .

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