The temperature of the inner core can be estimated using experimental and theoretical constraints on the melting temperature of impure iron at the pressure (about 330 GPa) of the inner core boundary, yielding estimates of 5,700 K (5,430 °C; 9,800 °F). The range of pressure in Earth's inner core is about 330 to 360 gigapascals (3,300,000 to 3,600,000 atm),and iron can only be solid at such high temperatures because its melting temperature increases dramatically at these high pressures