Longevity, projection, and sillage describe three different aspects of the same perfume, and they do not automatically increase together. Longevity tells you how long you can still smell it on your own skin, projection tells you how far the scent reaches around you while you stand still, and sillage is the trail of scent you leave behind as you move through a room. Once you separate the three terms, you can read a perfume description correctly and decide, from your own experience, how many sprays are worth using.
- Longevity is how long you can still smell the perfume directly on your skin, from application until it disappears completely.
- Projection is the distance from which another person can smell the perfume while you stand still, not while you are moving.
- Sillage is the scent that remains in the air after you have passed through a place, because you moved and carried it with you.
Longevity, projection, and sillage: three different things
When you read a perfume review, the three terms almost always appear together, but they answer different questions. Longevity matters to you: if you bring your wrist to your nose at 6 p.m., can you still smell anything of the perfume you applied in the morning? Projection matters to the people around you while you are sitting at your desk or at a table—how close does someone have to be to smell it? Sillage appears only when you move: when you pass someone in a hallway or get up from the table and leave behind a trail of scent that lingers for a few seconds after you have already left the room. The term comes from French, from the word for the trail left by a boat in the water, and it was adopted in perfumery precisely for that kind of trail that can be sensed even though it cannot be seen (source: Sillage - Wikipedia).
What depends on the perfume and what depends on you
Part of how strongly and how long a perfume can be smelled comes from its formula, not from how strong it smells when first sprayed. The concentration of perfume oil is the first factor: an Extrait de Parfum usually contains 15-30% perfume oil, an Eau de Parfum 15-20%, an Eau de Toilette 5-15%, and an Eau de Cologne just 2-3%, though the ranges vary slightly from one perfume house to another (source: Perfume - Wikipedia). The higher the concentration, the more aromatic molecules remain on your skin and are released gradually, which explains why an Extrait de Parfum lasts, on average, longer than an Eau de Toilette from the same family. The notes themselves matter just as much: top notes, usually citrus or aromatic, evaporate in the first few minutes and create the initial impression, while base notes—woody, ambery, musky—break down much more slowly and sustain the scent for hours after the top notes have already disappeared. If you want to see in detail how this kind of olfactory pyramid is built, the article about how a perfume is made, from raw materials to the final composition goes into the details of the process.
Your skin and the weather
The rest depends on you and the conditions around you. Oily skin holds perfume longer than dry skin because the natural lipids on your skin help the aromatic molecules stay there instead of evaporating quickly (source: Scento - How fragrance concentration affects sillage). Body heat and room temperature speed up evaporation, which is why the same application seems stronger and lasts longer on a cool autumn evening than on a hot summer afternoon. Pulse points—the wrists, neck, and backs of the knees—are warmer and help the perfume release steadily throughout the day, which is why they remain the recommended places to apply it, rather than clothes or hair.
Why a higher concentration does not automatically mean greater sillage
It is easy to assume that if an Extrait de Parfum has more perfume oil than an Eau de Parfum, it automatically smells stronger from a distance. In practice, things are more nuanced: very oily concentrations often project less, staying within a radius of about 0.3-0.5 meters around the skin, while versions with more alcohol in the formula diffuse more widely right from application because the alcohol evaporates quickly and carries the aromatic molecules farther into the air (source: Scento - How fragrance concentration affects sillage). Over the long term, however, the Extrait de Parfum wins on longevity: the cited benchmarks range from one to two hours for an Eau Fraîche to eight to twelve hours or more for an Extrait de Parfum.
The clearest way to see this is to compare the same composition in two concentrations, not two different perfumes. With the Baccarat Rouge 540 Duo: EDP and Extrait, you can experience how the exact same blend of notes changes when only the concentration is different: the Eau de Parfum tends to be more immediately noticeable around you after application, while the Extrait stays closer to the skin but lasts longer. The practical conclusion is that a higher concentration primarily buys you longevity, not necessarily greater projection from the very first minute. If you first want to understand each category on its own, the articles about Eau de Parfum, Eau de Toilette, and Extrait de Parfum cover each one in turn.
How many sprays are enough?
A general guideline that applies to most perfumes is four to six sprays for an Eau de Toilette, two to four for an Eau de Parfum, and one or two dabs for an Extrait de Parfum, applied to pulse points rather than sprayed excessively over the whole body (source: Scento - How fragrance concentration affects sillage). The right number also depends on the specific perfume, not just its category.
For Xerjoff Erba Pura, a cheerful perfume that is quite powerful by design, the product description even recommends just two sprays in summer during the day, which is enough without becoming overwhelming—a useful guideline especially for someone trying this perfume for the first time and not yet sure how powerful it really is. If, after an hour or two, you feel that your perfume has disappeared and are tempted to spray it again, it is worth knowing that your nose naturally adapts to a scent it is continuously exposed to and starts to smell it less and less, even if the people around you still perceive it just as clearly as they did at first. This phenomenon is called olfactory fatigue; it is temporary and passes on its own after a break. It does not mean the scent has disappeared from the air, only that your own nose has become used to it (source: Olfactory fatigue - Wikipedia). That is why an extra spray made “so it can be smelled” often does not change how others perceive you at all and only makes the bottle run out faster.
How to test all this before buying the full bottle
All these factors—concentration, base notes, skin type, weather, and number of sprays—are best checked on your own skin, on different days and during different activities, not in a single quick test at a perfume counter. Wearing a sample on an office day with air conditioning tells you something different from wearing the same sample on a summer evening spent outdoors, and the difference matters especially if you want a perfume to wear regularly, not just occasionally. Our decants are poured from original bottles specifically for this kind of repeated testing over several days, and the size guide shows how many sprays and roughly how many days of wear you get from a 2, 3, 5, or 10 ml decant, so you can choose the right size for the way you want to test it.
Choose a 2-3 ml decant of Xerjoff Erba Pura and notice how you adjust the number of sprays yourself as you learn how the perfume behaves on your own skin, instead of buying the full bottle straight away based only on a description.
