Full Circle - S18-E3
Corrected entry: Romana gives the TARDIS's weight as five million kilograms in the planet's gravity. This is totally inconsistent with the TARDIS's weight in the rest of the series - for instance, in the third Doctor's time, a few soldiers were enough to lift it. And it can't be because of the planet having high gravity, as the Doctor and Romana would have been killed and K-9 crushed whenever they went outside the TARDIS.
Correction: There is no mistake. The outside has always weighed less than the inside, just like the outside is always smaller than the inside. Its outside weight is dependent on its chameleon camouflage, but in this episode they're talking about the interior weight. There have been episodes where people were unable to pull it if the chains were on inside, and in the episode Castrovalva, the weight of the TARDIS is much greater than 5 million kg. If that immense weight was always the case, it would crash through the floor of many locations where it materialised.
Bishop73
Referring to the new series, in the Twelfth Doctor episode "Flatline", the Doctor outright says that if he landed the TARDIS on Earth at its full weight it would crack the planet's crust.