Need help with CSS breakpoints

[hallianonline]

Hello,
I want to know about the css breakpoints i searched on internet and get too many confusing results.
What my requirements are to place only 3 breakpoints which are as follow
to get the screen width of desktops and laptops
then to get screen width of tabs and ipads: portrait and landscape
then to get the screen width of smartphones: potrait and landscape
Please update me with the smallest and finest working example which will be compatible with all screen sizes.
Thanks

[hericles]

Bootstrap uses 3 breakpoints at 768, 992 and 1200px. Giving extra small (below 768), small (less than 992), medium (over 992) and large (over 1200).

[gabrielcastillo]

This is taken form foundation framework

@media only screen { } /* Define mobile styles */ 
@media only screen and (max-width: 40em) { } /* max-width 640px, mobile-only styles, use when QAing mobile issues */ // Medium screens 
@media only screen and (min-width: 40.063em) { } /* min-width 641px, medium screens */ 
@media only screen and (min-width: 40.063em) and (max-width: 64em) { } /* min-width 641px and max-width 1024px, use when QAing tablet-only issues */ // Large screens 
@media only screen and (min-width: 64.063em) { } /* min-width 1025px, large screens */ 
@media only screen and (min-width: 64.063em) and (max-width: 90em) { } /* min-width 1025px and max-width 1440px, use when QAing large screen-only issues */ // XLarge screens 
@media only screen and (min-width: 90.063em) { } /* min-width 1441px, xlarge screens */ 
@media only screen and (min-width: 90.063em) and (max-width: 120em) { } /* min-width 1441px and max-width 1920px, use when QAing xlarge screen-only issues */ // XXLarge screens 
@media only screen and (min-width: 120.063em) { } /* min-width 1921px, xxlarge screens */