One of the best UK websites with a free online pension calculator is the Hargreaves Lansdown website, which provides plenty of information to investors and individuals seeking to invest and make their money grow. Users can also access the pension calculator, a useful online tool that allows you to find out how much pension you can expect to receive. This website is found at https://www.hl.co.uk/pensions/interactive-calculators/pension-calculator/pension-calculator.