The 10 numbers you need to be smart with your money

That's the amount that gets withheld from the median household income of $46,000. Do you know how big a bite gets taken out of your paycheck for federal tax withholding, Social Security, and Medicare combined? How about the amount that's left after state and city taxes and other deductions for insurance and retirement? To calculate how much you net, pull out your pay stubs for the past month (if you're married, grab your spouse's docs too). You can't even begin to get a grip on spending and saving if you don't have a clear picture of what you're bringing in. Now you know.

The difference equals the percentage of your investments that should be in stocks; the rest should be in bonds. So a 35-year-old woman ideally has 65 percent of her money in stocks and 35 percent in bonds. Don't let recent market trends scare you--those who wait out the rocky times end up with more money than those who switch up their investments out of fear. If the market tumbles, you'll have time to let your portfolio rebound. You want to grow your money aggressively until you get close to needing the funds, which is why the ratio should slide toward more conservative, less risky bonds as you age. Reset the balance once a year on your birthday--or consider a "target date" mutual fund, which does it for you automatically.

Multiply that by your salary to determine how much life-insurance coverage you need, and your partner should do the same. Some employers offer group life insurance plans, but they're rarely customizable to fit your family's specific needs, and typically only pay for coverage equal to one to two times your salary. Compare rates for term-life policies that will protect your kids until they're grown at term4sale.com.

This is the national average for credit card interest rates. If you've got a card in your wallet with a higher rate, pay that balance off first, because you're getting slammed with major charges. The good news: Interest rates are generally negotiable. If you regularly pay at least the minimum on time, try haggling your way to a better rate, or consider moving the balance to your card with the lowest one--but do that only if you won't get socked with hefty fees for the transfer.

It's the minimum percentage of your salary that you should contribute to your 401(k) plan. Roughly 41 percent of workers at businesses with retirement plans get a match of up to 6 percent, says the U.S. Bureau of Labor Statistics; many companies put in between $.50 and a dollar for every buck you save. So if you make $50,000, you could be getting an extra $3,000 every year if your employer contributes dollar for dollar. Whether your company has a matching program or not, sock away up to 10 percent if you can--but start by making sure you never leave any free money on the table.

It's the maximum you can contribute to an individual retirement account, or IRA, each year. If you have a 401(k) through your job, make sure you're contributing at least 6 percent there. Then, if you can swing it, aim to put away the full $5,000 in an IRA to further expand your retirement savings and get sweet tax breaks. There are two types: a traditional IRA, which lets you defer paying taxes on the money and what it earns until you retire, and a Roth IRA, where you pay taxes on the contribution now, but the earnings are tax-free. My advice: Go with the Roth (which is only an option for couples earning less than $183,000), because it lets you tap into that money without penalty, if you need to, before your golden years.

That's the maximum percentage of your take-home pay that should go toward housing, including mortgage payments, insurance, and property taxes. Pre-recession, many experts put the figure at 33 percent, but in this unpredictable job market, that's too high. If you and your spouse make a combined $80,000, keep your new-home budget under $200,000. And if your housing expenses top the 25-percent mark, refinance your mortgage to lower your interest rate. You'll feel a huge financial lift once you can truly afford the roof over your head.

That's the amount to sock away each week in a savings account reserved for emergencies. You should have a six- to nine-month reserve in case you lose your job or face some other budget-blowing problem, but that goal can seem overwhelming. So start small with $50 a week. In one year, that's more than $2,500 saved, which will put you ahead of many households. One recent poll found that roughly one in four Americans wouldn't be able to come up with $2,000 in 30 days if they needed it. Start saving now.

The number of savings goals you should have. A recent University of Toronto study found that people who limit themselves to three goals under one theme--say, long-term saving--are three times more likely to say they'll save than those who have myriad competing goals, such as retirement, a super-luxe vacation, a new home, and college funds for your kids. We say: Focus on retirement and an emergency fund, and the last one is up to you--so pick something worth it!

That's the credit score you need to qualify for the lowest interest rate on a new home or car. It makes a huge difference: On a $300,000 mortgage, someone with a score of 760 or higher could get the best rate of 3.24 percent, which works out to roughly $1,304 a month. But if your score drops 100 points, your payment will shoot up another $100. Ouch. The best ways to raise your number? Pay all your bills on time and pay down your debt--those two things make up 65 percent of your score. To make sure there are no errors dragging you down, get your credit reports annually from each of the major credit-reporting agencies (Experian, TransUnion, and Equifax) for free at annualcreditreport.com.