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Each year brings new tax numbers. For example, for your 2014 tax return, when you're calculating your business-related travel deductions, the IRS mileage rate is $0.56 per mile, down from $56.50 last year. The allowed credit for the adoption of a child with special needs is $13,190, up from $12,970 in 2013. When it comes to saving for your retirement, there are lots of new numbers, too, including the 401k limits for 2014 contributions. 

For those who could use a quick review, 401k plans are offered by many employers, and they allow employees to save money on a tax-deferred basis. You contribute pre-tax dollars, reducing your current taxable income, and then are taxed on withdrawals in the future. There are also 403b plans, which are similar but designed for employees of public schools, churches, and certain nonprofit organizations. Finally, 457b plans are designed for employees of city, county, and state government entities, along with public schools and colleges.

2014 contribution limits for 401k, 403b, and 457b plans

Plan type

401k

403b

457b

Basic contribution limit

$17,500

$17,500

$17,500

Catch-up contribution for those 50 and older

$5,500

$5,500

$5,500*

Total contribution limit for those 50 and older

$23,000

$23,000

$23,000

*Not available to those who work for tax-exempt employers.

What to aim for

The 457b, 403b, and 401k limits for 2014 reflect how much you can contribute to your workplace retirement account. But how much you should contribute is a different matter. Don't just fall back on the old rule of thumb to sock away 10% of your income. That can be fine for those who start saving and investing while they're still young; but many of us have underfunded nest eggs. Just last month, the folks at Bankrate.com surveyed 1,003 adults and found that a whopping 36% haven't even started saving for retirement. Late starters will generally need to sock away considerably more than 10% of their incomes.

It helps to know how much you need to accumulate, too. Researchers Michael Finke and Terrance Martin have found that people with a financial advisor who calculated their retirement needs had saved 2.5 times more for retirement. A million dollars is often suggested as a retirement nest egg goal, but you might do fine with less.

So how much do you need to sock away? Here's a handy table from the Center for Retirement Research at Boston College:

Center For Retirement Research At Boston College
Source: Center for Retirement Research at Boston College.

The table shows, for example, that if you're aiming to replace 70% of your current income in retirement, and you're currently 45 and planning to retire at 67, you'll need to sock away 20% annually. You might even want to be conservative and aim higher in case life throws you a curve ball, such as an unexpected job loss.

Strategize

Once you're familiar with 401k limits for 2014 and have a sense of how much you need to accumulate and how much you need to sock away, it's smart to make the most of tax-advantaged retirement accounts such as 401ks and IRAs. A good rule of thumb is to first contribute to your 401k -- not up to the 401k limit for 2014, but only enough to get the maximum company matching funds. Then shift your savings to an IRA, which has its own 2014 limit of $5,500 for most of us and $6,500 for those 50 and older. Once you max that out, return to your 401k and take aim at the maximum contribution.

The reasoning is that IRAs give you far more flexibility in investment options, offering just about any stock or bond, plus ETFs and mutual funds. Further, a 401k will have a relatively small investment menu and may also have significant fees. Lastly, a Roth IRA permits tax-free withdrawals in retirement, while traditional 401k withdrawals are taxed.

It's smart to keep up on Uncle Sam's changing rules so that you can make the most of your retirement savings. Knowing the 401k limits for 2014, for example, can give you a goal to shoot for.

Longtime Fool specialist Selena Maranjian, whom you can follow on Twitter, has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.