General damages are not worked out from a formula, and there is no calculator that can tell you what your injury is worth. Instead, they are assessed. The starting point is the medical evidence. An expert examines you, reviews your records and reports on the nature of the injury, its severity and the prognosis, which means their view on how it is likely to develop. That report is then measured against the ranges used for injuries of comparable severity in the Judicial College Guidelines.
The guidelines give a bracket rather than a precise figure, and where you sit within that bracket depends on your own circumstances. The medical expert's view of severity and prognosis carries real weight. So does the practical effect on your life: whether the injury has interrupted your career, whether you need help you did not need before, and whether the activities that mattered to you have been lost or curtailed.
Your age and general circumstances are also relevant. The same injury can carry different consequences at different stages of life, and an injury that affects a young person's career or education may have a longer reach than one sustained later. Where an accident aggravated a condition you already had, the law takes you as you were found, so the fact that you were more vulnerable than the average person does not reduce what you can recover.
There is also the question of how long the effects are expected to last. An injury that resolves within a few months sits in a lower bracket than one with lasting or permanent consequences. That is why the medical evidence often needs to be updated before a claim is valued, and why settling before the picture is clear risks under-compensating you.
Where the accident was partly your fault, the total award, including general damages, is reduced by a percentage to reflect your share of the blame. That is known as contributory negligence, and it reduces the claim rather than defeating it.