The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 18-55mm f3.5-5.6 II and the Canon 15-85mm f3.5-5.6 IS USM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Canon 15-85mm f3.5-5.6 IS USM is the longer of the two lenses at 88mm. The Canon 18-55mm f3.5-5.6 II with a length of 80mm, is 8mm shorter. Besides being longer, the Canon 15-85mm f3.5-5.6 IS USM also has a larger diameter of 82mm compared to the Canon 18-55mm f3.5-5.6 II's 69mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Canon 18-55mm f3.5-5.6 II weighs 190g, which means it is 385g (66%) lighter than the Canon 15-85mm f3.5-5.6 IS USM which has a weight of 575g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Canon EF-S Mount for size comparison purposes.
Standard Lenses in Canon EF-S Mount for Size Comparison
Filter Threads
The Canon 18-55mm f3.5-5.6 II has a filter size of 58mm whereas the Canon 15-85mm f3.5-5.6 IS USM has a 72mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 58mm filters that we recommend you to consider for the Canon 18-55mm f3.5-5.6 II:
And these are the 72mm filters that we recommend for the Canon 15-85mm f3.5-5.6 IS USM:
Lens Mounts
Both the Canon 18-55mm f3.5-5.6 II and the Canon 15-85mm f3.5-5.6 IS USM has the same Canon EF-S lens mount. Some of the latest released cameras that are compatible with the Canon EF-S lenses are Canon T8i, Canon 90D and Canon SL3.
Focal Range
Canon 18-55mm f3.5-5.6 II has a focal range of 18-55mm and
3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-88mm when used on a APS-C / DX format camera.
On the other hand, the Canon 15-85mm f3.5-5.6 IS USM has a focal range of 15-85mm and 5.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 24-136mm when used on a APS-C / DX format camera.