The idea is not to show a specific amount as "balance" it is to show that you have steady income and expenses in the home country.
This shows that you have established ties.
For example, if each month there is rent deduction, credit card fees, car loan, interest payments, salary and then there are other normal transactions of someone actively living here - this is more important than an account that has a huge balance, but no transactions.
It is especially bad if you have a large influx of funds (called fund parking) and this can lead to outright rejection of your application. So please don't borrow money just to prop up your bank account.
The idea when showing funds is that showing you have access to funds so that you can cover the expenses of your trip.
This means you can show that for example, the flight is paid for by your host, and you have _______ in UK pounds in cash; you have _______ UK pounds available to you in savings and an additional _______ UK pounds on your credit card that you can utilize.
For converting, use onada.com and mention the rate used.
Keep in mind that the officer is trying to determine if you are trying to immigrate illegally. Any kind of obligations that you have on you, or family ties, or a business are evidence that you are unlikely to stay beyond your remit.
They are very keen on signs of deception - such as large deposits and things like having a mountain of paperwork as supporting documents; so please don't try to pad your application.