When successful, waxing removes hair from the root and can last up to six weeks. However, skin isn't always hair-free for a full six weeks. In fact, most people actually see regrowth much sooner. How quickly hair regrows depends on several factors: the average hair growth cycle, your personal hair growth cycle, breakage, and how frequently you get a wax.
There are three stages of hair: growing, resting, and transitional. At any given time, approximately 80 to 90 percent of hair follicles are in the growth phase. The rest are either in the transitional phase (two to three percent) or in the resting phase (10 to 15 percent). This means that, whenever you get waxed, there's probably some hair underneath the skin growing, and it hasn’t reached the surface yet. It can even be above the skin and not long enough to be grasped. In this scenario, waxing isn't going to be able to grasp these hairs and remove them. In the next few days or weeks to come, these hairs will become noticeable, although how noticeable depending on their thickness and color. Even if the hairs are the same length, dark and thick hair will start to show much sooner than light and fine hair.
Different areas of the face and body don't spend the same amount of time in their phases of growth, rest, and transition. Biological sex has also been found to affect the amount of time spent in the hair growth phase—even in the same body area. Age, season, hormone levels, and genetics also play a big part of these personal cycles. You'll also notice or feel thick or dark hair (like in the bikini line) much more than fine and light facial hair re-growth. Ultimately, this means that your leg waxing won't necessarily last you the same amount of time as your friend's, nor will it grow back in sync with the bikini wax you got on the same day.
How often you get waxed also helps to determine how long you can expect your wax to last. If you get waxed every two to four weeks, then all hair will have had the chance to be removed from the root. You'll then notice that your skin is staying hair free longer, and you'll be able to go longer between appointments. Someone that gets waxed (or uses any method that removes hair from the root) regularly will often cause the follicle to become damaged over time. This may also cause a reduction where it comes back finer or just stops growing altogether. How soon that would happen after being repeatedly waxed will vary depending on the person, their age, genetics, and the specific area at hand.
In a perfect world, with ideal circumstances and fail-proof technicians, each and every hair would be successfully removed from the root every time. Unfortunately, that's not realistic. When hair is being waxed, it tends to break off above or even below the skin's surface sometimes. The length of hair, the type of wax used, the quality of wax used, and skill of the technician all can affect whether the hair will break. Although professionals can break the hair, it's much more likely that you will do so yourself if you do your own at a home session. Hair that is broken has not been removed from the follicle, so you'll see hair much sooner than you thought you would when this happens. If it broke above the skin, then the results will last comparably to shaving. If it broke below the skin, you have a couple of days before you see it.
Because breakage creates a sharp edge, often ingrown hairs follow—use an all-natural oil product post-hair removal to prevent and heal them.
Ultimately, you're at the mercy of your body when deciding to schedule your next wax. You'll only really be able to guess how frequently you should schedule your appointments after you've had a few of them already.