There's a lot you can negotiate in a new job offer: your salary, of course, but also your job title, start date, a signing bonus, and maybe the most fun to plan for — your paid time off.

It's one benefit Sherri Carpineto, 48, says she "always" negotiates for at this point in her career.

Carpineto is currently a senior director of operations for a health-care company and lives in Boston. She also offers career coaching services and often helps professionals with their negotiation strategy.

If you get a job offer and you're not happy with the amount of PTO in the package, Carpineto says there are three ways you can negotiate for more:

1. Negotiate for what you already have

First, if the PTO on offer is less than what you're used to, you can base the number of days you want on what you're getting from your current or a previous employer. Let the recruiter know that's the amount you've worked with before and how it's contributed to your continued success at work.

2. Calculate PTO based on your needs

Second, Carpineto says you can negotiate for a number based on your own calculations of what you need. For example, do you need a set number of days off to observe religious events that aren't federal holidays?

This can be especially helpful for parents and caregivers. Get to know your child's school year, when school is not in session, and when you'll need more flexibility.

If the company uses one PTO bank, don't forget to consider your own health needs and account for sick or personal days throughout the year.

3. Research your industry and competitors

Finally, Carpineto says that if the PTO on offer is low for your industry, you can pull that research into the conversation and ask for what you've found to be standard in your field.

For even more leverage, you might research the PTO allotment at a competitor business to show that you're basing your negotiation on another policy that already exists.

How to figure out if a company really supports time off

If it's important to you to work for a company that supports employees taking time off, Carpineto suggests finding ways to ask about it early on.

For example, you could ask the hiring manager or another interviewer the last time they took a vacation. How did the team prepare? Did they feel fully supported in taking time off?

If a company offers unlimited PTO, Carpineto recommends asking about the average amount of time people take off. Does that company require workers take a minimum number of days off? Or do they offer any mandatory "quiet periods," like around the holidays or otherwise?

Ultimately, when negotiating your salary and benefits, the most important place to start is knowing your must-haves versus your nice-to-haves, Carpineto says. Apply them to the benefits you want but also generally to the role — what you need and want from your job, your team, your boss and the company overall.

Want to earn more money at work? Take CNBC's new online course How to Negotiate a Higher Salary. Expert instructors will teach you the skills you need to get a bigger paycheck, including how to prepare and build your confidence, what to do and say, and how to craft a counteroffer.

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