How the US Income Percentile Calculator works
This tool answers a specific question: given an annual income, roughly what share of US households earn less — and what share earn more? Exact answers require the Census Bureau's raw survey microdata, which is not something a page of JavaScript can query in real time. Instead, this calculator uses the standard shortcut economists reach for when only summary statistics are available: it fits a lognormal distribution to the income data using two published numbers — the median household income and the Gini index (a 0-to-1 measure of income inequality) — and reads your percentile off that fitted curve.
The formula
A lognormal distribution means the natural log of income is normally distributed. Two parameters define it: μ (the mean of log-income) and σ (its standard deviation). Because the median of a lognormal distribution equals eμ, we get μ directly from the median you enter:
μ = ln(median income)
The Gini index of a lognormal distribution has a known closed form, G = 2Φ(σ/√2) − 1, where Φ is the standard normal cumulative distribution function. Solving for σ:
σ = √2 · Φ−1((G + 1) / 2)
Once μ and σ are known, your percentile is just the standard normal CDF applied to the standardized log-income:
percentile = Φ((ln(income) − μ) / σ) × 100
The calculator also inverts the same formula to report the income threshold for the 90th percentile: income90 = eμ + σ·Φ−1(0.90).
Where the default numbers come from
The calculator pre-fills a median household income of $83,730 and a Gini index of 0.49, both from the US Census Bureau's report "Income in the United States: 2024" (Report P60-286), based on the 2025 Current Population Survey Annual Social and Economic Supplement covering calendar year 2024 income for all US households. Both fields are editable — enter a different year's figures, a state-level median and Gini, or statistics for a different reference group (such as individual earners) if you have them, and the same formula applies.
Worked example
At the default settings, an annual income of $75,000 against a $83,730 median and 0.49 Gini index works out to roughly the 45th percentile — modestly below the midpoint, consistent with the income being below the median. Raising the income to $150,000 with the same reference statistics pushes the estimate to roughly the 73rd percentile, and $250,000 lands around the 88th percentile — illustrating how the lognormal curve compresses near the median and stretches out at higher incomes.
Why this is an approximation, not an exact lookup
Real income distributions are not perfectly lognormal — they tend to have a fatter right tail than the lognormal curve predicts, meaning this model can understate just how exclusive the very top percentiles (the top 1% or top 0.1%) actually are. It also treats "income" as a single number without adjusting for household size, region, or age, all of which real Census tables break out separately. Treat the result as a solid, transparent estimate of where you sit in the broad middle of the distribution, and treat estimates near the extreme tails as directional rather than precise.