Last updated: May 17, 2026
fetch() and you're done.Access-Control-Allow-Origin: *)._meta.lastUpdated ISO date.All endpoints accept GET requests and return application/json.
Marginal tax rates and bracket cutoffs for single, married-jointly, married-separately, and head-of-household filers, plus standard deduction amounts.
fetch('https://calc-center.party/api/data/tax-brackets-2026.json')
.then(r => r.json())
.then(data => console.log(data.filingStatuses.single));National average rate + APR for 30-year fixed, 15-year fixed, 5/1 ARM, FHA, VA, and jumbo loans.
fetch('https://calc-center.party/api/data/mortgage-rates.json')
.then(r => r.json())
.then(data => data.products.forEach(p =>
console.log(p.name + ': ' + p.rate + '% (' + p.apr + '% APR)')));WHO adult BMI ranges from underweight through obese class III, each with min/max, color, risk level, and description.
const { categories } = await (await
fetch('https://calc-center.party/api/data/bmi-categories.json')).json();
const myBmi = 24.1;
const cat = categories.find(c => myBmi >= c.min && (c.max === null || myBmi < c.max));
console.log(cat.label); // "Normal weight"Five training zones (recovery, fat-burn, aerobic, anaerobic, max) with %HRmax ranges. The Karvonen formula is documented in _meta.formula.
const res = await fetch('https://calc-center.party/api/data/heart-rate-zones.json');
const { zones } = await res.json();
const age = 30, hrMax = 220 - age;
zones.forEach(z => console.log(
z.name + ': ' + Math.round(hrMax * z.minPercentHRmax/100) + '-' +
Math.round(hrMax * z.maxPercentHRmax/100) + ' bpm'));Five activity levels (sedentary 1.2 → extremely active 1.9) with descriptions and concrete examples.
const r = await fetch('https://calc-center.party/api/data/tdee-activity-multipliers.json');
const { levels } = await r.json();
const bmr = 1650;
levels.forEach(l => console.log(l.label + ': ' + Math.round(bmr * l.multiplier) + ' kcal'));Compounding period n values (daily 365 → annually 1) for use in A = P(1 + r/n)^(nt).
const r = await fetch('https://calc-center.party/api/data/compound-interest-frequencies.json');
const { frequencies } = await r.json();
const monthly = frequencies.find(f => f.id === 'monthly');
console.log('n =', monthly.n); // 12Trimester week ranges (1st: 1-12, 2nd: 13-26, 3rd: 27-40) with average weight gain, milestones, and common symptoms.
const r = await fetch('https://calc-center.party/api/data/pregnancy-trimesters.json');
const { trimesters } = await r.json();
const week = 22;
const current = trimesters.find(t => week >= t.startWeek && week <= t.endWeek);
console.log(current.label); // "Second Trimester"30 major world currencies with ISO code, name, symbol, decimal places, and region.
const r = await fetch('https://calc-center.party/api/data/currency-symbols.json');
const { currencies } = await r.json();
const eur = currencies.find(c => c.code === 'EUR');
console.log(eur.symbol + ' ' + (1234.56).toFixed(eur.decimals));Full working snippet — paste into any HTML file. Calculates the marginal bracket for a given income and writes it to the DOM.
<div id="result">Loading...</div>
<script>
const income = 85000;
const status = 'single';
fetch('https://calc-center.party/api/data/tax-brackets-2026.json')
.then(r => r.json())
.then(data => {
const brackets = data.filingStatuses[status];
const bracket = brackets.find(b =>
income >= b.min && (b.max === null || income < b.max)
);
const pct = (bracket.rate * 100).toFixed(0);
document.getElementById('result').textContent =
'$' + income.toLocaleString() + ' (' + status + ') → ' +
pct + '% marginal bracket';
})
.catch(err => console.error('API error:', err));
</script>Have a use case we haven't covered? Need historical data, a different country's tax brackets, or a private dataset? We're open to suggestions.
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