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VAT Calculator

Adds VAT at a given rate to a net price, or removes it from a gross (VAT-inclusive) price, returning net, VAT and gross amounts.

When to use

You need the VAT-inclusive price for an invoice, or the net price and VAT portion of a gross amount, at a known rate such as 20 % (UK), 19 % (Germany) or 21 % (Netherlands).

Do not use when: You are dealing with US sales tax terminology (use sales-tax; the arithmetic is identical), or with multiple rates on one invoice (compute each line separately).

Formula

add_vat: vat = amount × rate/100, gross = amount + vat. remove_vat: net = amount / (1 + rate/100), vat = amount − net

Inputs

Parameter	Type	Unit	Required	Description
`amount`	number		yes	Net price (mode=add_vat) or gross VAT-inclusive price (mode=remove_vat). Range: ≥ 0, ≤ 1000000000
`vat_rate_percent`	number	%	default 20	VAT rate in percent; standard rates in the EU range from 17 % to 27 %. Range: ≥ 0, ≤ 100
`mode`	enum: add_vat \| remove_vat		default add_vat	Whether amount is net (add) or gross (remove).

Outputs

Output	Type	Description
`net_amount`	number	Price before VAT.
`vat_amount`	number	net_amount × rate.
`gross_amount`	number	net_amount + vat_amount.
`vat_fraction_of_gross`	number	rate / (100 + rate), e.g. 1/6 at 20 %: multiply a gross price by this to get the VAT.

Example

100 net plus 20 % VAT: {"amount":100,"vat_rate_percent":20,"mode":"add_vat"} → {"net_amount":100,"vat_amount":20,"gross_amount":120,"vat_fraction_of_gross":0.166667}

119 gross, remove 19 % VAT: {"amount":119,"vat_rate_percent":19,"mode":"remove_vat"} → {"net_amount":100,"vat_amount":19,"gross_amount":119}

GET https://tttkmbb.com/api/v1/calculate/vat?amount=100&vat_rate_percent=20&mode=add_vat

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/vat (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/vat · Markdown: https://tttkmbb.com/finance/vat.md · JSON definition: https://tttkmbb.com/finance/vat.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="vat"
OpenAPI operationId: calculate_vat
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Wikipedia – Value-added tax (reference)
GOV.UK – VAT rates (government)
European Commission – VAT (rates and rules in the EU) (government)

FAQ

What is the VAT fraction?

The share of a gross price that is VAT: rate / (100 + rate). At 20 % it is 1/6, so the VAT in a 120 gross price is 20, not 24.

Which rate applies?

Standard rates apply to most goods; reduced or zero rates apply to items such as food, books or children's clothing depending on the country. Check the national tax authority's list.

Related calculators

Sales Tax Calculator — US-style sales tax with the same arithmetic.
Margin and Markup Calculator — Set a net selling price from cost before adding VAT.