A stamp duty calculator is a tool that helps you figure out how much tax you need to pay when you buy a property in the UK. The tax is called stamp duty land tax (SDLT), and it depends on how much the property costs and whether you're a first-time buyer or buying it as your primary residence. The calculator takes these factors into account and gives you an estimate of how much tax you'll need to pay. This can help you plan your budget and make an informed decision when buying a property.