Where the numbers come from

Every figure the calculators use, where it comes from, and what it leaves out. Everything below was checked on October 24, 2026.

Premium tax credit rules

What	Figure	Source
2027 applicable percentages	2.15% under 133% of the poverty line, rising to 10.22% from 300% to 400%	IRS Rev. Proc. 2026-26, Internal Revenue Bulletin 2026-31
2026 applicable percentages	2.10% to 9.96%	IRS Rev. Proc. 2025-25
Income limit	100% to 400% of the poverty line for 2026 and 2027	26 U.S.C. 36B(c)(1); the 2021 to 2025 exception expired and no 2026 law revived it
Repayment of excess advance credit	No cap from tax year 2026	Pub. L. 119-21, section 71305
Immigrant eligibility	Narrowed in 2026 and 2027	Pub. L. 119-21, sections 71301 and 71302
Below 100% with advance payments	Still treated as eligible	26 CFR 1.36B-2(b)(6)

The credit is the benchmark plan’s annual premium minus your income times the applicable percentage, never less than zero and never more than the premium of the plan you buy. Within each income band the percentage rises in a straight line, as 26 CFR 1.36B-3 describes.

Poverty guidelines

Year	48 states and DC	Alaska	Hawaii	Used for
2026	$15,960 + $5,680 per person	$19,950 + $7,100	$18,360 + $6,530	2027 marketplace credits; 2026 Medicaid and CHIP
2025	$15,650 + $5,500 per person	$19,550 + $6,880	$17,990 + $6,330	2026 marketplace credits

Source: HHS poverty guidelines published in the Federal Register on January 15, 2026 and January 17, 2025, and the ASPE table.

County premiums

County benchmark, bronze, silver and gold prices come from CMS’s individual market plan file (the QHP Landscape file) for plan year 2026, published on data.healthcare.gov and re-posted August 26, 2026. It covers the 2,055 counties in the 30 states that used HealthCare.gov for 2026. CMS had not posted the 2027 file as of October 24, 2026.

The benchmark is the second-lowest-cost silver premium offered in the county for a 40-year-old non-smoker. Other ages are priced with CMS’s default age curve (a 64-year-old pays 3 times a 21-year-old) or the state’s own curve in Alabama, DC, Massachusetts, Minnesota, Mississippi, Oregon and Utah; New York and Vermont don’t rate by age. Only the three oldest children under 21 in a family are charged, as federal rules require.

In 18 counties some plans cover only part of the county, so the benchmark depends on the ZIP code. The calculator and state pages flag those counties.

Medicaid and CHIP limits

Limits by state come from MACPAC’s MACStats (February 2026, Exhibits 35 and 36, data as of July 2025), which compiles CMS’s eligibility levels and state plan amendments. Changes since then are taken from the state agency: DC (January 1, 2026), New York’s Essential Plan (July 1, 2026), Minnesota, Oregon and South Carolina. Limits include the 5-point income disregard, as Medicaid agencies publish them. Where KFF’s January 2026 survey differs, the difference is noted in our data file.

Exchanges and enrollment dates

Exchange type for 2027 is from CMS’s list of state-based marketplaces (updated August 14, 2026). HealthCare.gov’s dates are from its dates and deadlines page. Each state-run exchange’s dates are from its own 2027 announcement. The shortened 2027 open enrollment in the 2025 Marketplace Integrity rule was vacated by the U.S. District Court for the District of Maryland on June 16, 2026 (City of Columbus v. Kennedy); the government has appealed.

Special enrollment and COBRA

Special enrollment windows follow 45 CFR 155.420 as of October 22, 2026, and the 2027 Notice of Benefit and Payment Parameters (91 FR 29526). COBRA rules follow the Department of Labor’s employee guide and 26 CFR 54.4980B-6.

What the calculators don’t do

They don’t use 2027 premiums yet, model state-funded subsidies, add tobacco surcharges, or handle households whose members live in different places. They estimate; the marketplace and the IRS decide. Questions or corrections: use the contact form.