There are so many foot shapes out there, and almost as many heel options, too! Any sock knitter will quickly discover that some heel construction styles and shapes work better for them than others. I'm going to start with a caveat: I am a strong proponent of trying lots of heel shapes and experimenting with a variety of heel fit "tweaks" as the primary way of making a wide variety of heels work, because you deserve to have lots of options for heels that fit you, and to not be exasperated every time a lovely pattern that catches your eye uses the "wrong" heel!

But, that said, heel substitution is also an option you should have in your sock-knitting toolbox; there are bound to be styles of heels that just don't work for you, at all, and that are difficult to adjust significantly to make them fit better. In those cases, a substitution to a heel you're very familiar with and comfortable making can be the right choice. Substituting can sometimes be difficult, though, depending on how deeply opinionated you are about exactly how you prefer to construct your sock heels. Let's talk about the easy ways first, and then move on to more complex substitutions after that.

The most straightforward option for heel substitutions is swapping between no-gusset heels, since these kinds of heels all will fit into the pattern the same way: they are all inserted between the sole and back of leg, over approximately half of the stitches, as a kind of interruption in the sock patterning. You stop working the main patterning, make the heel (or mark where the heel will go later), then return to the main patterning. This group of heel shapes includes both afterthought heels and (most) short-row heels.

The most important thing to keep in mind for these kinds of heel substitutions is the differences in heel depth between the pattern's recommended heel and the one you want to use. That's the whole benefit of substituting, after all; to change the shape and depth of the heel to make it work better for your foot! Make sure to adjust for your row gauge and (especially when working toe-up, but when working afterthought heels this is important in both knitting directions) adjust your planned foot length accordingly to make sure you don't end up with a great-fitting heel, but a foot that's too long or too short.

This is the easiest heel substitution of all time, to the point where I don't really consider it a "substitution" at all! I talk about re-shaping an afterthought heel in this article on heel fit tweaks; all you have to do is follow the pattern instructions until you have the heel stitches ready to go on the needles, then use whatever shaping style — pointed like a second toe, rounded, adding short rows to the corners, etc. — works best for you.

As an aside, if you're concerned about getting the length of the foot right (don't forget about adjusting for the all-important row gauge!) when you're making changes to an afterthought heel's depth and/or shaping, don't forget — there's no rule that says you must make the heel at the very end of the socks! You can always just work 5-10 rounds past a scrap yarn afterthought heel marker (I show what this "forethought heel", no-cutting-the-yarn-necessary technique looks like and how to pick up the heel stitches in this video), to secure it in place, then put the stitches for the body of the sock on a holder and make the heel "early". This will give you a chance to try it on before you've committed to finishing the socks; for cuff-down socks in particular it eliminates the worries about foot length entirely, because if the heel is already there, you only need to know when to start the toe. (For toe-up socks, this does help reduce the amount of ripping-out necessary if you need to fix the foot length, which is much better than working the whole leg before realizing the foot is too long or short. However, depending on the patterning on the sock you're making, you might prefer to try the "toe-up, but make the toe last" strategy I talk about at the end of this article instead, for a frogging-free "easily tweak the foot length at the last minute" knitting experience.)

Rounded "Eyeball" Afterthought Heel

Heel With Afterthought Gussets

This sounds like an easy substitution, but it can actually be a bit of a minefield. As long as your preferred heel and the heel in the pattern are both worked over only the back of leg/sole stitches, and without gusset shaping, all you need to think about is heel depth adjustments, and (especially if you're working toe-up) row gauge. But if you're working on a pattern that uses something like a "Boomerang" Heel (which has rounds in the middle of the heel that go all the way around the instep) or a "Sweet Tomato" Heel (which is designed to be worked over more than half of the stitches, including some from the instep), replacing one of them with a different short-row heel will be less straightforward, unless you're making a completely-vanilla sock. It might make more sense to try using a heel fit tweak to improve the fit instead of making a substitution, particularly if the pattern is complex and the heel's structure is a significant design feature.

On the flipside, if you want to replace a more traditional short-row heel with one of those "invades the instep" short-row heels, it will be more complicated than just knitting to the point where you need to turn the heel and then following a different set of instructions; you will need to be comfortable enough with the sock pattern's principles to be able to manage either more stitches in the heel shaping or more rounds worked during the heel that include all of the instep. And, fair warning, swapping to an instep-invader heel will make a much bigger aesthetic change in the overall finished product than a substitution for a different half-the-stitches short-row heel would.

In most cases, this substitution is as simple as putting a scrap yarn placeholder instead of a short-row heel, then coming back to it at the end to make an afterthought heel instead. The only complication is being able to predict your new heel depth. Regardless of whether you're working toe-up or cuff-down, afterthought heels require you to leave the right amount of room for them when you're making your sock foot. If you know how deep your afterthought heels normally are (as you probably do, if they're one of your favourite heel types), this isn't a huge thing to handle, but watch your row gauge, especially if you're using a yarn that's new to you.

This is almost as easy as substituting an afterthought heel for a short-row heel! Make sure, especially if you're working toe-up in this case, to adjust for differences in predicted heel depth and row gauge. And be careful — not all short-row heels allow for the kind of plug-and-play substitution you might be looking for. Any short-row heels that invade the instep (such as a "Boomerang" Heel or a "Sweet Tomato" Heel) are not going to seamlessly sub in for an afterthought heel. Plus, in rare cases afterthought heels are used by designers for their much easier potential for adding heel patterning; if this is the case in the pattern you're making, you'll need to make the sock as-written (though possibly with fit tweaks, depending on the type of patterning involved) if you want to maintain the integrity of that design detail. A short-row heel construction will not allow you to easily work things like stripes or stranded colourwork, but an afterthought heel will.

One interesting thing about this substitution is you can even do it at the very end of making the sock. You can pick up your stitches for an afterthought heel like you normally would, but then you can make a sort of "I'm having second thoughts about an afterthought heel" decision and make a short-row heel instead! Just put the stitches from above the heel (so, the leg stitches for toe-up construction and the foot stitches for cuff-down construction) on hold, and work the heel on the bottom stitches only. When you're done the heel shaping, graft the heel stitches with the stitches you put on a holder, and the heel is complete! You will want to leave long enough ends at each side of the heel to make sure the heel corners are cleaned up and hole-free, but it is definitely possible to work a short-row heel that way, if you plan to make an afterthought heel but then change your mind at the last minute.

"Chinstrap" Short-Row Heel

Patterned Afterthought Heel

The more shaping you add to (or subtract from) a sock, the more complex it gets to substitute a different heel. There are lots of heel fit tweaks you can use for gusset-and-heel-flap construction to customize the fit, but if you're looking to make major changes — even substituting different styles of gusset-and-heel-flap heels can be complicated, let alone swapping between heels with and without gusset shaping — that takes some sock-construction experience and some decision-making about how you want your finished socks to look. The more detailed the sock pattern is, the more decisions you have to make about how different your heel-substitution socks will look from the original pattern sample, and the more work you're going to have to do on your own to handle the math and logistics of making your new heel choice work.

Wait, there are multiple kinds of gusset-and-heel-flap heels? Absolutely! The most common variations are what I call a "Traditional" Heel, plus the "Fleegle" Heel and the "Strong" Heel. And here's where I put forward my personal hot take on this kind of heel shape: I think the latter two are essentially the same and I'm going to treat them that way. The only significant difference between them is that "Fleegle" Heels were initially designed for toe-up socks and "Strong" Heels were initially designed for cuff-down socks. When toe-up patterns say they use a "Strong" Heel, it is shaped like a "Fleegle" Heel, and when cuff-down patterns say they use a "Fleegle" Heel, it is shaped like a "Strong" Heel. The structural differences between them are, at most, very subtle, and more dependent on the individual designer's construction choices than the name of the heel. So, if you like either one of those heels, I guarantee you'll like the other one too, since it's the same overall shape and requires the same skills.

"Traditional" Heels have a square/rectangular heel flap that is typically reinforced with slipped stitches, short rows are used to shape the bottom of the heel turn, and gusset shaping is done on the foot. Working cuff-down, the heel flap is worked flat, then stitches are picked up on the sides of the flap to make the gusset stitches, which are then decreased on the foot. Toe-up, the gussets are formed with increases on the foot, and then the gusset stitches are integrated into the heel flap using decreases, so no picking-up is required. Toe-up "Fleegle"/"Strong" Heels are similar, with gusset increases on the foot but with a heel flap that isn't rectangular (more of a trapezoid, with the connection between heel flap and gusset stitches on a diagonal instead of a vertical line because the decreases are worked in the centre of the heel flap instead of at the sides) and that generally does not include reinforcement stitches. Cuff-down "Strong"/"Fleegle" Heels are essentially upside-down versions of the same thing; the main difference from other gusset-and-heel-flap heels is that they have gusset increases on the back-of-leg part of the heel, beside the stitches that would make up the heel flap in a "Traditional" Heel, and the gusset decreases are done on the sole, making that part of the sock structurally more of a "heel flap" than the part at the back of the leg is.

Most toe-up patterns won't even blink if you choose a different style of gusset-and-heel-flap heel for your sock. All of the most common variations have gusset increases on the foot somewhere (either on the sides of the instep or the sole of the foot, most of the time, though it is possible to find them in other places occasionally), and the only significant difference is how the heel flap is shaped. This is rarely going to have any impact on the design of the socks; just watch for differences in the number of rounds of gusset increases (as this will affect how much room you leave in the foot length before you start increasing) and make sure you adjust to have the correct stitch count in the end once you get to the leg patterning. You're only going to encounter issues if the heel flap is part of the patterning, and that's relatively unusual — even designs with patterned gussets are potentially compatible with this kind of substitution without too many issues, as long you aren't making a change to the overall number of increases, just to the shape of the heel turn and flap.

Cuff-down patterns are a little bit trickier for this kind of substitution, because swapping gusset-and-heel-flap types in this direction usually means moving the gusset areas around. If the pattern has a "Traditional" Heel and you want to use a "Strong"/"Fleegle" Heel, you need to add gusset increases on the leg while still working the full circumference, and when trading "Strong"/"Fleegle" Heels for "Traditional" Heels, you need to omit those gussets and figure out how much overall leg patterning you need to do before working a separate, worked-flat heel flap. Moving the gusset shaping to a different part of the sock will change the overall look of the sock, and it won't be easily compatible with any patterning the designer may have incorporated into the gusset areas. A sock pattern with a "Traditional" Heel isn't expecting you to insert plain triangles into its leg patterning, and a sock pattern with a "Strong"/"Fleegle" Heel will have gusset decreases in a different area than a "Traditional" Heel typically does (sole versus sides of the instep). While on vanilla or nearly-vanilla socks all of this is not a big issue, since the areas in question (sole, gussets, back of leg) are likely all plain stockinette stitch anyway, for more complex patterns, making it look like the design elements work with those kinds of major overall-construction changes can require a lot of sock-knitting experience and additional work.

Easy To Shift Gussets

More Difficult to Shift Gussets

If you want to use a short-row heel or an afterthought heel instead of a gusset-and-heel-flap heel while working cuff-down, in a lot of cases this is not too complicated. When working a cuff-down pattern that has a "Traditional" Heel, you can simply start the short-row heel (or place the afterthought heel marker) where the pattern tells you to start the heel flap. You will have to watch the instructions to make sure you get the right stitch count for the foot — some patterns get you to pick up stitches from the leg beside the heel flap, for example — and then you'll need to be able to identify and ignore all the foot instructions related to gusset decreases. If you're substituting an afterthought heel, you'll also need to leave room in your foot length for it when deciding when to start the toe shaping.

When working any gusset-and-heel-flap pattern toe-up, or working a cuff-down pattern that uses a "Strong"/"Fleegle" Heel, the concept works the same way: ignore the instructions about increasing for the gussets and instead work until you have the right depth remaining for your preferred heel, then make that heel instead. The most challenging part of this substitution is lining up the patterning between the foot and the leg. Getting this transition right is one of the hardest parts of designing more complex socks, and small changes in the number of rounds or the overall stitch count can easily put you in a position to have to figure out the math and logistics the designer did originally all over again on your own.

One big, huge caveat to all the above is patterned gussets. While a lot of patterns have plain gussets that are essentially part of the sole of the sock, some integrate patterning into the gussets, and stranded-colourwork socks in particular often can't have gussets unless they have some sort of patterning, because otherwise the floats get too long. While in some patterns you could omit the gussets without anyone noticing the difference, in other cases this might require changing or removing whole motifs, altering the overall look of your socks significantly and losing some of what attracted you to the design in the first place. Patterned heel flaps are an issue too; although this is less common than patterned gussets, it certainly happens in sock designs, and losing that section might create aesthetic and logistical issues for the finished product.

Patterned Gussets

Patterned Heel Flap

If you are one of those people who says, "If I can't make it with a gusset and heel flap, I'm not making it," this is for you! (However, I really, really recommend that you consider experimenting with heel fit tweaks as well, because you deserve to have more choices for comfortable sock heels, and I guarantee that there are other heel types that will fit you right, even if they need a few little adjustments.) Be aware that is the most complicated substitution to achieve, since it requires adding whole sections to a sock pattern that doesn't have them in the original instructions. At a minimum, you need to have some experience with how socks are constructed in general, and you need to be very familiar with the gusset-and-heel-flap heel you're substituting into the pattern, in order to make this work. And if you're making a more complex sock, you're going to need to be comfortable with all the techniques involved (especially if stranded colourwork is required) in order to be able to extrapolate/adjust the motif(s) to accommodate the stitches you're adding to the circumference by inserting gussets.

(Even if the pattern is relatively simple, but it omits gussets for an obvious reason — designs that manipulate self-striping yarn or pooling yarn and therefore require a very consistent stitch count, for example — you may lose that desired effect or find the patterning just doesn't work properly anymore if you insert gussets into the design. For those kinds of patterns, I recommend trying a more subtle heel fit tweak instead, if the heel in the pattern doesn't work well for you.)

Substituting a "Traditional" Heel is relatively straightforward when working cuff-down. Simply start your heel flap where the pattern says to work the no-gusset heel, work the flap and turn as you prefer to work it, and then decrease your picked-up gusset stitches as you work the foot. As long as the sole is plain, the inserted gusset stitches can be plain too, and they will fit right into the design of the sock. However, all bets are off if you're working with something like a stranded-colourwork pattern that depends on a consistent stitch count to make a wider motif work; then you're entering the realm of having to make not just sock-construction changes but also substantial design alterations.

if you want to substitute a "Strong"/"Fleegle" Heel cuff-down, you will need to add gusset increases to the leg, which many patterns with a motif that is worked around the entire leg will not easily accommodate. Again, you'll not only need to work different heel instructions, but also create new patterning on the sock from scratch. Your best option for an easy substitution is where there is a plain back of the leg, or possibly a pattern where there is a clear division between the back of leg and front of leg motifs.

When working toe-up, this substitution is all about row gauge and overall gusset-and-heel-turn depth. You're going to want to refer to the math I provide in this article to help you figure out where to start working gusset increases. Don't skip the row-gauge math; gusset-and-heel-flap construction needs much more space than a short-row heel or an afterthought heel, and therefore small differences in row gauge will have a much bigger impact on fit. If the sole of the sock is plain, the gusset stitches can be plain, too, and they will blend right into the sock; however, if you decide to insert gusset stitches in a pattern that includes patterning on the sole (such as stranded-colourwork designs), you are going to have to be more creative with what you do in those extra stitches to make sure the sock construction still works well and the project looks the way you want when it's finished.

Easier To Add Gussets

More Difficult To Add Gussets

If this all feels very overwhelming, you might prefer to try a less extensive (but often no less effective!) heel adjustment by using a fit tweak rather than a full-blown substitution. Ultimately, making major construction changes to a sock pattern is something that requires experience, skill, and a willingness to adapt, fudge, and frog things until they work out well enough for you to be okay with the results. Especially if you're just starting out in sock knitting (though I recommend this to everyone who knits socks, experienced or not), it's worth making lots of different heels, just to try them out on your foot and see how you like them, and learning about little adjustments you can make for an improved fit. Deciding that you're only going to substitute your one favourite heel into every pattern you knit is not the only option out there for getting socks that fit!