{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"sales-tax"},"result":{"entity_type":"calculator","id":"sales-tax","calculator_id":"sales-tax","canonical_url":"https://tttkmbb.com/finance/sales-tax","name":"Sales Tax Calculator","title":"Sales Tax Calculator – Add Tax to a Price or Extract Tax from a Total","category":"finance","category_name":"Finance","tool_name":"calculate_sales_tax","featured_mcp_tool":false,"description":"Adds sales tax at a given rate to a pre-tax price, or works backwards from a tax-inclusive total to the pre-tax price and the tax paid.","use_when":"You need the checkout total for a price and a combined state/local sales-tax rate, or want to know how much of a receipt total was tax.","do_not_use_when":"The tax is a value-added tax quoted as net/gross (use vat, which is the same arithmetic with VAT terminology), or you need the tax rate for a specific location (look it up first).","inputs":[{"name":"amount","label":"Amount","type":"number","required":true,"min":0,"max":1000000000,"description":"The pre-tax price (mode=add_tax) or the tax-inclusive total (mode=extract_tax).","example":100},{"name":"tax_rate_percent","label":"Sales tax rate","type":"number","unit":"%","required":true,"min":0,"max":100,"description":"Combined sales-tax rate in percent (state + local), e.g. 8.25.","example":8.25},{"name":"mode","label":"Mode","type":"enum","required":false,"default":"add_tax","values":[{"value":"add_tax","label":"Add tax to a pre-tax price","aliases":["add","forward","exclusive"]},{"value":"extract_tax","label":"Extract tax from a tax-inclusive total","aliases":["extract","remove","reverse","backward","inclusive"]}],"description":"Whether amount excludes tax (add) or already includes it (extract).","example":"add_tax"}],"outputs":[{"name":"pre_tax_amount","label":"Pre-tax amount","type":"number","decimals":2,"description":"Price before sales tax."},{"name":"tax_amount","label":"Sales tax","type":"number","decimals":2,"description":"pre_tax_amount × rate."},{"name":"total_amount","label":"Total with tax","type":"number","decimals":2,"description":"pre_tax_amount + tax_amount."},{"name":"tax_share_of_total_percent","label":"Tax as share of total","type":"number","unit":"%","decimals":2,"description":"tax_amount / total_amount × 100 (lower than the rate, since the rate applies to the pre-tax price)."}],"input_schema":{"type":"object","properties":{"amount":{"description":"The pre-tax price (mode=add_tax) or the tax-inclusive total (mode=extract_tax).","type":"number","minimum":0,"maximum":1000000000,"examples":[100]},"tax_rate_percent":{"description":"Combined sales-tax rate in percent (state + local), e.g. 8.25. Unit: %.","type":"number","minimum":0,"maximum":100,"examples":[8.25],"x-unit":"%"},"mode":{"description":"Whether amount excludes tax (add) or already includes it (extract).","type":"string","enum":["add_tax","extract_tax"],"default":"add_tax","examples":["add_tax"]}},"additionalProperties":false,"required":["amount","tax_rate_percent"]},"output_schema":{"type":"object","properties":{"pre_tax_amount":{"description":"Price before sales tax.","type":"number"},"tax_amount":{"description":"pre_tax_amount × rate.","type":"number"},"total_amount":{"description":"pre_tax_amount + tax_amount.","type":"number"},"tax_share_of_total_percent":{"description":"tax_amount / total_amount × 100 (lower than the rate, since the rate applies to the pre-tax price). Unit: %.","type":"number","x-unit":"%"}}},"formula":"add_tax: tax = amount × rate/100, total = amount + tax. extract_tax: pre_tax = amount / (1 + rate/100), tax = amount − pre_tax","sources":[{"name":"Wikipedia – Sales tax","url":"https://en.wikipedia.org/wiki/Sales_tax","type":"reference","retrieved_at":"2026-09-23"},{"name":"Investopedia – Sales Tax: Definition, Examples and How It's Calculated","url":"https://www.investopedia.com/terms/s/salestax.asp","type":"reference","retrieved_at":"2026-09-23"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"100 plus 8.25 % tax","inputs":{"amount":100,"tax_rate_percent":8.25,"mode":"add_tax"},"expected":{"pre_tax_amount":100,"tax_amount":8.25,"total_amount":108.25,"tax_share_of_total_percent":7.62},"url":"https://tttkmbb.com/api/v1/calculate/sales-tax?amount=100&tax_rate_percent=8.25&mode=add_tax"},{"name":"108.25 total, extract 8.25 % tax","inputs":{"amount":108.25,"tax_rate_percent":8.25,"mode":"extract_tax"},"expected":{"pre_tax_amount":100,"tax_amount":8.25,"total_amount":108.25},"url":"https://tttkmbb.com/api/v1/calculate/sales-tax?amount=108.25&tax_rate_percent=8.25&mode=extract_tax"}],"faq":[{"q":"Why can't I extract tax by multiplying the total by the rate?","a":"Because the rate applies to the pre-tax price: 108.25 × 8.25 % = 8.93, not 8.25. Divide the total by 1.0825 to get the pre-tax price first."},{"q":"Which rate do I enter?","a":"The combined rate that applies at the point of sale: state plus county, city and special-district rates. It varies by location and product type."}],"tags":["sales tax","tax calculator","price plus tax","reverse sales tax","pre-tax price"],"related":[{"calculator_id":"vat","reason":"The same calculation with net/gross VAT terminology and rates."},{"calculator_id":"discount","reason":"Apply a discount and then tax."},{"calculator_id":"tip","reason":"Add a gratuity to a bill."}],"links":{"html":"https://tttkmbb.com/finance/sales-tax","markdown":"https://tttkmbb.com/finance/sales-tax.md","json":"https://tttkmbb.com/finance/sales-tax.json","api":"https://tttkmbb.com/api/v1/calculate/sales-tax","schema":"https://tttkmbb.com/api/v1/calculators/sales-tax","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:31:32Z"}