Savers are buzzing about the new Roth Individual Retirement Account. Roth IRAs start up in January and will let you take investment gains from stocks, bonds, mutual funds or savings accounts entirely tax free.

But deciding whether to use a Roth isn’t as simple as it sounds.

You’ll probably have at least two retirement plans to choose from. There’s more than one way of calculating which plan will yield more, and the experts disagree.

The basic rules for Roth IRAs are clear. Workers can salt away up to $2,000 a year ($4,000 for married couples). You cannot tax-deduct the money. You’re funding this plan with after-tax dollars.

The full contribution is available to singles with adjusted gross incomes under $95,000 and couples under $150,000. Singles can make partial contributions on incomes up to $110,000 and couples up to $160,000.

You can take out your own contribution, tax free, anytime you want. You also get the earnings tax free if you hold the IRA at least five years and withdraw the money under one of the following circumstances: you’re over 59 1/2; you’re taking up to $10,000 to buy a first home; you’re disabled; or your heirs take the IRA after your death.

Should you use the Roth instead of some other retirement plan?

I’ve put together some of the things you should think about.

For employees with company 401(k) plans:

– If your company matches the money you put in, invest enough to get the maximum match.

– If you can afford to put the maximum into two retirement plans, fund a Roth IRA and a 401(k).

– If you don’t get an employer match, consider putting up to $2,000 of your retirement contribution into a Roth IRA and the rest into your 401(k). (For when to make this choice, see below.)

The 401(k) retains one big advantage. Payroll deduction forces you to save the money, whereas Roth contributions depend on your personal discipline.

For the self-employed:

– You have a variety of tax-deductible plans available a simplified employee pension (SEP), a Keogh plan, and a SIMPLE IRA. All of them allow larger contributions than you’d have with a Roth.

– If you can spare enough income, put the maximum into a deductible plan and fund a Roth IRA, too.

– If you can’t fund two plans in full, a Roth IRA might make sense for the first $2,000 you put aside.

For anyone trying to decide between putting $2,000 into a Roth or into a tax-deductible plan:

– If you’re in the same tax bracket when you retire, the Roth IRA beats the tax-deductible plan, says Steve Norwitz of the mutual-fund company T. Rowe Price in Baltimore. The younger you are when you start the Roth, the better it will turn out to be.

If you’re in a significantly lower bracket at retirement, however, the deductible plan would probably come out ahead, especially for older investors.

T. Rowe Price’s analysis compared investing $2,000 into a Roth, after tax, with investing $2,000 in a deductible plan and building up a separate fund with your income-tax savings every year.

Financial planner Lynn Hopewell of the Monitor Group in Fairfax, Va., has a different take. When he compared the two plans, he adjusted for taxes by reducing the amount you put into the Roth. In the 33 percent bracket, for example, $2,000 after tax comes to $1,340 so that’s what Hopewell assumed you invested.

Using this calculation, the Roth and the tax-deductible plan deliver the same amount of income, if your tax bracket remains the same after retirement.

The Roth is better if your tax bracket will be higher in retirement. The deductible plan is better if your bracket will be lower in retirement, Hopewell says.

Both of the above are valid ways of doing the math. As a practical matter, however, you’ll probably put the full $2,000 into the Roth. So you’d get the results T. Rowe Price predicts.

Price is offering a free worksheet for figuring out whether a Roth or tax-deductible IRA is better for you (call (800)333-0740).

To make the comparison by computer, go for Price’s new IRA Analyzer ($9.95; for Windows 3.1 and up and an IBM-compatible computer with a 486 processor or greater). With minor modifications, it’s free on the Web site www.troweprice.com.

Treasury Direct

If you buy Treasury securities, it just got easier. You now have many more options when you invest through the government program called Treasury Direct.

The changes may save you money and will definitely make it easier to buy, sell and reinvest.

Under Treasury Direct, you purchase securities through the Federal Reserve. You pay no fees or commissions, as you would if you bought through a stockbroker or bank.

To buy Treasuries, there’s now a single “tender” form to fill in, for all types of Treasury securities bills, notes and bonds. Formerly, you needed a separate form for each type.

When you mail in the tender form, you can also authorize the Treasury to deduct the cost of the investment from your account at a bank, brokerage firm or mutual fund. The debit is made on the day your security is issued, so your savings will earn interest without interruption.

Formerly, you had to send in a certified or cashier’s check with your order which is still OK, if you prefer it. But the new system saves you a trip to the bank as well as several days of lost interest earnings.

The Treasury charges no fees for this electronic debit, but some financial institutions do, so check it out. Also check to be sure that your designated account can be debited electronically.

Your interest earnings are paid directly into your account. Ditto your principal, when your securities mature.

If you’re interested in Treasury Direct, write to the nearest Federal Reserve Bank for a packet of information, call the automated public-information number at the Bureau of the Public Debt at (202)874-4000 (choose the menu for “forms”) or dial up Treasury Direct on www.publicdebt.treas.gov.

Syndicated columnist Jane Bryant Quinn can be reached in care of the Washington Post Writers Group, 1150 15th St., Washington D.C. 20071-9200.