Radhanath Sikdar (Bengali: রাধানাথ শিকদার; 5 October 1813 – 17 May 1870) was an Indian mathematician who is best known for calculating the height of Mount Everest. He was the first person to calculate the height of Mount Everest, in 1852. Great Trigonometric Survey In 1831, George Everest, the Surveyor General of India, was in the pursuit of a mathematician who had specialised in Spherical Trigonometry, so that they could be a part of the Great Trigonometric Survey. In 1832, under the leadership of Everest, the longitudinal series of the "triangle" survey was completed from Seronj in Madhya Pradesh to Calcutta in West Bengal. While still working on mapping Calcutta, Bengal, Everest had begun his search for a mathematician, and soon enough, John Tytler, a professor of Mathematics at the Hindu College, now known as the Presidency College, recommended his 19-year-old pupil, Radhanath Sikdar. Radhanath, a student of the college since 1824, was one of the first two Indians to read Isaac Newton's Principia and by 1832; he had studied Euclid's Elements, Thomas Jephson's Fluxion and Analytical Geometry and Astronomy by Windhouse. Taking inspiration from these prestigious papers, he devised a new method to draw a common tangent to two circles, when he was just a teenager. There was little doubt about Radhanath's proficiency in his subject, and he secured the job at the GTS on 19 December 1831 as a "computer" at a salary of thirty rupees per month. Soon he was sent to Sironj near Dehradun. Even as seven other Bengali ‘computers’ worked alongside him, Radhanath soon showed his superior skills in mathematics and became Everest’s favourite colleague. So much so, that he once stopped his transfer to another department. Radhanath’s job was to carry geodetic surveys—the study of the earth’s geometric shape orientation in space and gravitational field. He did not just use the established methods but invented his own to accurately measure these factors. George Everest retired in 1843 and was succeeded by Colonel Andrew Scott Waugh. Eight years later, in 1851, Radhanath was promoted to the position of Chief Computer and transferred to Calcutta. Here, he was also a superintendent for the Meteorological Department. At the order of Colonel Waugh, Radhanath started measuring the height of mountains. The brilliant mathematician, who had perhaps never seen Mount Everest, discovered in 1852 that Kangchenjunga, which was considered to be the tallest in the world, wasn’t really so.