An independent Line 4(c) calculator, built to get the two-job number right.

Who runs this

Line 4C.com is published by Red Goggles LLC, an independent operator of free web calculators and reference tools. We are not the IRS, not a payroll provider, not a tax-prep company, and not affiliated with any employer. We don’t sell anything, we don’t collect leads, and we don’t take your information — the calculator runs on your device and nothing you type is sent to us.

Why this site exists

The IRS already solves the two-job under-withholding problem on paper, in Step 2(b) of the Form W-4 — the Multiple Jobs Worksheet and its Table 1. But the worksheet makes people do a grid lookup and then divide by their pay periods by hand, and that division is where most people give up or get it wrong. Search snippets can show you the static annual Table 1 value, but they can’t take your two salaries and turn them into the per-paycheck number you actually write in the box. That gap — the proration, plus the fact that you fix it on one form without telling either employer about the other — is the entire reason this tool exists.

How it’s calculated

The estimate follows the IRS Multiple Jobs Worksheet, applied in the open:

• Table 1 lookup (Form W-4, Step 2(b)). We read the two-job grid keyed by your higher salary, your lower salary, and your filing status — the same grid on the current-year Form W-4 (fw4.pdf). There are separate grids for Married Filing Jointly (and Qualifying Surviving Spouse), Single/Married Filing Separately, and Head of Household; we read the one that matches your status. The cell where your salaries meet is an annual additional-withholding amount.
• The per-paycheck division. The number that goes on Line 4(c) is that annual amount divided by your pay periods (52 weekly, 26 biweekly, 24 semimonthly, 12 monthly). If you’re filing the W-4 mid-year, you can divide over the pay periods remaining this year instead — the same catch-up approach described in IRS Publication 505 — and we label clearly which basis the result uses.
• One form, higher-paying job. The extra withholding goes only on the W-4 for your higher-paying job; the other job’s W-4 stays at its default. That’s both the correct mechanic and the privacy point.

The method is spelled out on the calculator page under How it works, and the calculator shows the annual amount and the division so you can see the math.

How we stay accurate and current

Table 1, the Form W-4, and the figures that feed them are reissued every year. We transcribe the grid from the current-year Form W-4 PDF at irs.gov — not from a competitor’s page or a prior year — and we carry a visible “Last updated” date and the tax year the result reflects. Being correct for the current year is table stakes for a tax tool, so we treat re-verifying the grid and the pay-period conventions against the primary IRS source as a routine, dated task, not a one-time thing.

How the site is funded

Line 4C.com is free and supported by display advertising. Advertising is kept calm and never mixes with your inputs — see our privacy page for exactly what is and isn’t collected.

Questions or corrections? We take accuracy seriously on a topic that hits your paycheck — reach us on the contact page.