My GPA for my bachelor's degree here in the Philippines is 1.4259 (equivalent to magna cum laude). In the UK system, to which honors class will it belong?
Converting from one grading scheme to another is a nightmare: How to convert from one grading scheme to another?. In general, you should try and avoid trying to calculate an exact GPA in another system. That said, many US universities have a hard cutoff of a 3.0 GPA and many UK universities have a hard cut off of a 2.1 degree classification. Within these constraints, it seems reasonable to ask if a particular GPA in one system is clearly above, clearly below, or near the minimum admissions bar.
In the UK, there is an attempt to normalize the degree classifications across different universities. This is done by having external examiners on the exam board to prevent grade inflation. At Russell Group universities, about 10-15% of students get 1st class degrees and over 70% of students will get a 2.1 or higher. At lower ranked universities, fewer students will get first and upper second class degrees. Assuming a reasonably respectable university in the Philippines without rampant grade inflation magna cum laude would be well above the 2.1 bar and would probably be close to the 2.1/1st cut off.