Congratulations. You’ve been offered a new CFO job. But there remains the matter of evaluating the pay package.

If it’s a great offer, or if it’s a poor one, you can probably decide fairly easily whether you should take it, assuming you’re comfortable with your future colleagues and the new company’s business model, level of stability, and culture. “But there is a big gray area in the middle,” says Howard Seidel of Essex Partners, who provides compensation and career-management consulting services to senior executives.

Your thought process in that gray area will differ significantly according to whether you already have a job or if you’re in (what’s delicately called) transition. When a recruiter calls an employed finance executive, both parties know the offer will have to be pretty good to entice a move. Many CFOs look for a minimum 20% bump-up to move, most other things being equal.

On the other hand, people who are between jobs may be more likely to say yes, and wonder later whether they’ve said yes to a lowball offer because the hiring company had the leverage of knowing they didn’t have a job, Seidel notes.

Fortunate jobseekers who get multiple offers can simply compare them to one another, which should be a fairly simple task. When presented with the more difficult challenge of evaluating a single offer, the biggest question is whether to take it given “the great unknown” of what additional job offers or other factors might arise in the coming weeks, months, or year.

Against that backdrop, Seidel advises clients to evaluate the offer using the following three comparative measures.

One is called external equity, or how the offer aligns with similar-level positions at comparable companies. “What does the market pay for this job?” is what most people think about when deciding whether an offer is good, Seidel notes. A lot of information on specific CFO compensation packages at publicly held companies is, of course, available in their public filings. But while a candidate for a private-company job will find the going harder, there are ways to attack the issue.

First, looking at the compensation paid by public companies of similar size in the same industry can offer some insight. Some useful data may also be culled from the extensive, industry-specific research performed by Aon Hewitt subsidiary Radford. Sometimes companies themselves may provide some comparative information, like a data-based rationale for the offer: “We’re aiming to be in the 65th percentile of this group of companies.” Candidates should ask to see the specific data rather than just a summary, says Seidel.

Also, if you have good relationships with recruiters, even one that is representing the potential hiring company, they may steer you in the right direction to help you evaluate the offer.

All that said, there are many variables that can influence the package. What a candidate judges to be market value may not align with what the company is willing to pay, particularly in terms of salary. For example, less-mature companies, especially start-ups, often limit base pay and provide greater performance-based bonuses and equity opportunities that will (if the company becomes successful) more than make up the difference. (At mature companies, a common breakdown of pay components is one-third apiece for salary, bonus, and equity, Seidel says.)

The second measuring stick is called internal equity, or how the offer compares with similar-level roles inside the new employer. CFO candidates might be willing to take less than market if intrigued by the role, and if there’s an opportunity for compensation to expand later, but only if they believe they are being treated fairly in terms of what the CEO, COO, and other top executives are getting.

“It’s usually not in the company’s best interest to lowball you on an offer, because it knows that soon after you start the job you’re going to be able to look under the hood and know what everyone else earns and what their deals are,” says Seidel. “But that does happen, such as if a company puts out an offer and the candidate quickly accepts it while the company was expecting that there would be discussions.”

Finally, there is personal equity, or what the executive is currently making, if employed, or was making in his or her previous job, if in transition. “Recruiters want to know, in detail, about your compensation package because then they’ll know what it’s going to take to pull you out. Some companies have a rule not to bump anyone up more than [a certain percentage],” says Seidel.

But be aware of personal equity’s bigger picture. “If you’ve been making $500,000 and now somebody’s going to pay you $250,000, your history has changed,” notes Seidel. “In this economy, it’s not always possible to surpass or even equal your former package. But you can be ‘made whole’ in a number of different ways.” Sometimes that may mean taking a disproportionate amount of equity from a start-up, but that’s still “a relevant conversation to have,” he says.