To calculate the melting point of methane, you can use the following equation:

```

T_m = (1 / (4.3304 + (0.2443 * log10(P)))) - (0.0082 * log10(P)^2)

```

Where:

* T_m is the melting point in Kelvin

* P is the pressure in atmospheres

For methane at a pressure of 1 atmosphere, the melting point is approximately -182.5 °C (90.6 K).