About MFJ Tools

MFJ Tools was built to solve a frustration that almost every married couple runs into: figuring out how taxes work when two people file together. The official IRS withholding estimator is clunky, the rules around joint vs. separate filing are easy to get wrong, and most online calculators assume a single filer.

We built a focused set of free, no-signup calculators that handle the most common questions couples actually ask:

• If we both work, how should we set up our W-4 withholding?
• Should we file jointly (MFJ) or separately (MFS)?
• Are we paying a marriage penalty — or getting a marriage bonus?
• Roughly how much will we owe based on our combined income?

Who runs this site?

MFJ Tools is an independent project. We are not a tax preparation firm, and we don't sell any service. The site is funded by ads and occasional affiliate referrals to tax software, which keeps the calculators free.

How accurate are these calculators?

The calculators use current federal tax brackets, standard deduction amounts, and common credits. They produce reasonable estimates for typical situations. They do not handle every edge case — if you have complicated income (self-employment, equity compensation, foreign income, K-1s, etc.), use the calculators as a starting point, then talk to a tax professional about specifics.

Feedback

Spotted a bug or want a calculator we don't have yet? Email us via the contact page.