IRA calculator: traditional vs Roth

Compare a traditional IRA, where you save tax now, with a Roth IRA, where withdrawals are tax-free.

Pre-tax amount you can invest each year

Your tax rate now

Your tax rate in retirement

Years until you withdraw

years

Return

% a year

About the ira calculator: traditional vs roth

Compare a traditional IRA, where you save tax now, with a Roth IRA, where withdrawals are tax-free.

Part of SmartCalcy’s retirement tools. It runs in your browser with no account, uses your own currency and units (change them at the top of the page), and gives estimates for information only, so check official guidance before you rely on a result.

How to use the ira calculator: traditional vs roth

What it calculates and when to use it

Compares a traditional IRA (tax relief now, tax on withdrawals) with a Roth IRA (no relief now, tax-free withdrawals) given your tax rate now and in retirement.

How to use it, step by step

Enter the pre-tax amount you could invest each year.
Enter your tax rate now and your expected tax rate in retirement.
Enter the years until you withdraw and the expected return.

What each input means

Pre-tax amount – What you could invest before tax. A Roth contribution costs the same after-tax amount.
Tax rates – Your marginal rates now and in retirement.

How to read the results

Traditional after tax – The pot minus tax at your retirement rate.
Roth pot – The after-tax contributions’ growth, all tax-free.
Winner and difference – Which is better and by how much.

The formula

Traditional = contributions growing at r, then × (1 − retirement rate). Roth = contributions × (1 − current rate) growing at r. Both use end-of-period annuity-due growth.

A worked example

Investing 7,000 before tax at 24% now, with an 18% rate in retirement, 7% growth and 25 years: the traditional IRA nets 388,463 after tax and the Roth 360,039, so traditional wins by 28,424.

Assumptions and limits

The tax rates do not change within the periods.
The same amount of after-tax money is spent in both cases.
Income limits and deduction rules may apply.

Common mistakes

Assuming the Roth is always better.

Frequently asked questions

What if tax rates are equal?

The two end up the same. The Roth then offers flexibility and no required minimum distributions.

Dated rules: US federal figures for tax year 2026 (IRS Rev. Proc. 2025-32 and IRS notices). These calculators are estimates for planning, not tax advice.

Traditional IRA comes out ahead by

£28,424

after tax, when you take the money out

Details

Traditional: pot: £473,735
Traditional: after tax in retirement: £388,463
Roth: pot, all tax-free: £360,039
Contribution into a Roth each year: £5,320the same cost to you after tax

A Roth wins if your tax rate in retirement is higher than now; a traditional IRA wins if it is lower. With equal rates the two are the same. Income limits and deduction rules may apply to you.