This is a basic calculator that takes into account primary assets and liabilities. The estimated tax liability may be subject to variation as a result of tax planning, PETs and so on.
This calculator does not include any increase in the IHT allowance to which you might be entitled if you are the surviving spouse and your deceased's estate did not fully use the available annual exemption.
The nil-rate band is £325,000 for 2016/17. Anything which exceeds the £325,000 threshold will be taxed at 40% (though there are exemptions and reductions available).