Mid-calf and knee-high boots are hard to fit when their circumference is wider than your calf. The visual of a stem in a flower pot comes to mind. In some cases the gaps are intentional, and tend to work best with slouchy boot styles. The gaps work less well with boots that are supposed to create a tailored fit around the lower leg.
As a gal with a 13 inch calf measurement, I know how hard it can be to find tall boots that create a snug fit around the lower leg. One solution is to wear boot liners, leg warmers, or knee-high socks to “fill the gap” around the top of the boots. Pull the socks above the tops of the boots, then scrunch them down to close the gap. Leg warmers, in particular, are a great way to create bulk on the calf but not on the foot.
The photos below show examples of boot liners and leg warmers peeking out from the tops of boots worn with skirts and dresses. But feel free to wear the same boot and sock combination over skinnies, leggings or jeggings. You’ll create a fun textural interest and layered effect on the leg line, which works especially well with chunkier knitwear and casual outerwear.
Keep the socks low contrast or the same colour as the boots so that they are an extension of the boots. Match black or charcoal socks with black boots, and brown socks with brown boots. Alternatively, keep the socks low contrast or the same colour as the pants so that they appear to be an extension on the pants. For example, wear burgundy boot liners or leg warmers with burgundy skinnies and tall black boots. You can also create a high contrast between both the pants and the boots, which can be a fun look if you don’t mind the horizontal break across the leg line.
The sock filling technique is best suited to casual and smart casual wear, and is less fab with dressy outfits or formal career wear. The visual effect is also quite maximal and heavy, which might not be your cup of tea if you prefer a simple and streamlined look. That said, purchasing an inexpensive pair of boot liners or leg warmers might make an existing pair of ill-fitting boots wearable by masking the gap. It also might make you purchase a pair of casual boots that are perfect in every respect except for a calf circumference that is too wide.