Required Margin - does each broker have its own value?

Hi everyone.

I am trying to figure out the ‘value’ of a particular trade and have been reading : What is Margin? - BabyPips.com

If i want to place a micro lot order (1000) on GBP/USD - this article suggests the required margin is 5%.

However when I place trades using my platform, it seems to suggest my margin is $33.33 given a balance of around $10000

A bit confused so trying to work it out.

Micro lot is 1000.
Balance is 10,000.

10000/100 * 3.33 = 333.

Trade is 0.01 - 1000GBP

333 / 100 = 3.33

This maths to me is just muddling with numbers until i arrive at the $33.33 margin that the trade is reporting.

Can somebody split it into a more clear forumla? An article I have been reading suggests:

When I try to replace this with my numbers I get:

(1000*1.24305) 3.33 + (10000.000018) = 4,139.3745 – where on earth am I going wrong!

Additionally, are currency pair required margins static, or are they set by each broker?