There is two major frameworks Bootstrap (by Twitter) and Foundation (by Zurb)they are the most used ones web frameworks. I recommend to start over there to see the sizes. Here is the code and sizes they use.
Bootstrap
/* Extra small devices (phones, less than 768px) */
/* No media query since this is the default in Bootstrap */
/* Small devices (tablets, 768px and up) */
@media (min-width: @screen-sm-min) { ... }
/* Medium devices (desktops, 992px and up) */
@media (min-width: @screen-md-min) { ... }
/* Large devices (large desktops, 1200px and up) */
@media (min-width: @screen-lg-min) { ... }
Foundation
// Small screens
@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 */
I personal use Sketch 3 and start with 850px desktop and mobile 320px
Here is one template 3 also for Sketch google bootstrap-3-responsive-grid-template.sketch (I can not paste more than 2 links)