Best Hair Growth Serum by Ingredients and Size

The best hair growth serum for volume is The Ordinary Multi-Peptide Serum for Hair Density, a 2.02 fl oz clear leave-in that lists more named actives than anything else here. If you want to spend the least, the Marc Anthony Grow Long serum matches that 2 fl oz size at the lowest price of the five. One caveat up front: none of these bottles publishes a measured volume result, so "volume" here means what the formula targets, not a proven lift.

How I narrowed the field to five

I lined up the published specifications and application methods side by side, then cut anything that didn't fit a scalp-focused density routine. Three things drove the shortlist.

• Format clarity. Four of the five are leave-in serums; one is a spray. That changes how you apply it and how fast a bottle empties.
• Ingredient transparency. I kept picks whose listings name specific actives, from peptides to biotin to rosemary oil, so you can match a formula to your own scalp.
• Bottle size on the label. Sizes here run from 1 fl oz to 5.07 fl oz, a fivefold spread that decides value more than any marketing line.

What got cut was vagueness. A listing that promised thickness without naming a single ingredient didn't make it. The five below all state what's inside and how to use it, which is the least you should demand from a scalp serum. Read the "volume" claim as a formulation goal, not a lab-confirmed outcome, because none of these listings carries a measured density figure.

Best hair growth serum for volume at a glance

Does a serum actually add volume?

Here's the honest answer. A serum can make hair look fuller in two different ways, and they aren't the same thing.

The first is coating. Viviscal's listing says its formula "coats each hair strand creating multi-dimensional density," which is a styling effect you'd notice quickly. The strand gets a little wider, so a head of hair reads as denser. That works on the hair you already have.

The second is scalp support over time. The Ordinary, Marc Anthony and Psalmonica all describe supporting follicles or roots, which is a slower game measured in months, not minutes. Moerie's listing even states you "should start to see stunning results" in 30 days and more by three months.

Neither route is proven by any figure in these listings. Treat the coating claims as short-term cosmetic and the follicle claims as long-term maintenance. The best hair growth serum for volume for you depends on which of those two you're actually after. If you need thicker-looking hair for an event next week, coating wins. If you're playing the long game, scalp formulas are the point.

1. The Ordinary Multi-Peptide Serum for Hair Density — Best overall

A 2.02 fl oz clear leave-in that names more actives than anything else in this group.

Best for: someone who wants the most ingredients per drop and a simple once-daily routine Skip it if: you want a spray or a quick styling boost

What sets this pick apart in the set is the ingredient stack. The listing names REDENSYL, Procapil, CAPIXYL, BAICAPIL, AnaGain and high-solubility caffeine, six peptide-family actives, plus plant extracts like Larix Europaea wood and pea. No other serum here lists that many named technologies. The Ordinary calls it a lightweight leave-in that supports the scalp for thicker, denser-looking hair.

The routine is deliberately simple. A few drops on a clean, dry scalp once daily, ideally at bedtime. At 2.02 fl oz it's the second-largest bottle here, behind only the 5.07 fl oz Moerie spray. The formula is listed as vegan, cruelty-free, alcohol-free and silicone-free, which matters if your scalp reacts to those.

This is the pick that sells fastest of the five in its listing. The trade-off: it sits in the pricier half of this group, and it's scalp-focused, so it won't give you the instant coating effect a strand-wrapping serum does. You're buying formula depth, not a same-day look.

Pros:

• Six named peptide actives, the deepest list here
• Second-largest bottle at 2.02 fl oz
• Vegan, alcohol-free and silicone-free
• Simple once-daily bedtime routine
• The fastest seller of the five

Cons:

• Priced in the upper half of this set
• Scalp-only, no instant coating effect
• Requires daily consistency to matter

2. Marc Anthony Grow Long — Best budget pick

The lowest price of the five at a full 2 fl oz, aimed at breakage along the length.

Best for: spending the least while targeting breakage down the length of your hair Skip it if: you want a scalp-only density treatment

Marc Anthony is the cheapest pick here and it doesn't cut the bottle to get there. You get 2 fl oz, matching The Ordinary almost exactly on size while sitting at the bottom of the price ladder. Released in 2023, it's the newest listing of the group.

The angle is different from the peptide serums. The listing describes strengthening hair fibers at the root and reducing breakage along the length, blended with caffeine, ginseng, rosemary oil, biotin and vitamin E. Marc Anthony also tells you to apply it to the lengths, not just the scalp, for moisture and shine. So this is as much an anti-breakage treatment as a density one, which suits someone whose "thin" hair is really snapped, damaged hair.

It's listed free from sulfates, parabens and phthalates. The trade-off against the pricier picks is a shorter and less technical ingredient story: caffeine and biotin rather than six named peptide complexes. If you want the most cosmetic chemistry per bottle, this isn't it. If you want the most milliliters per dollar, it's the clear call.

Pros:

• Lowest price of the five
• Full 2 fl oz, same class as the winner
• Works on lengths, not just scalp
• Free from sulfates, parabens, phthalates
• Newest listing, released 2023

Cons:

• Shorter, less technical ingredient list
• More anti-breakage than pure density
• Styling-serum category, not a regrowth tonic

3. Viviscal Hair Thickening Serum — Most versatile

The one pick that promises an instant coating effect as well as a leave-in treatment.

Best for: wanting thicker-looking strands right away without heavy product Skip it if: you want a peptide-based long-term formula

Viviscal earns "most versatile" because its listing works on two timelines at once. It's a lightweight leave-in that, in the brand's words, "instantly coats strands for thicker, fuller-looking hair" while also being a treatment you keep using. That instant-coating claim is the only one of its kind in this group, and it's the closest thing here to a same-day volume result.

The formula is built on biotin and keratin, fortified with marine collagen and seaweed extract, per the listing. Viviscal frames it as appropriate for women noticing changes in hair density. It's paraben-free, SLS-free and SLES-free.

At 1.69 fl oz it's the second-smallest bottle here, larger only than the 1 fl oz Psalmonica. It also sits in the lower price tier, so you're not paying premium money for the coating trick. The trade-off is ingredient depth: keratin and collagen are strand-conditioning agents, not the follicle peptides The Ordinary leans on. Choose this when you want the look today and the maintenance as a bonus, rather than the other way around.

Pros:

• Only pick claiming an instant coating effect
• Biotin, keratin and marine collagen blend
• Lower price tier despite brand name
• Paraben-free, SLS-free, SLES-free
• Lightweight, listed as not weighing hair down

Cons:

• Second-smallest bottle at 1.69 fl oz
• Conditioning actives, not follicle peptides
• Slower seller than the top two here

4. Moerie Hair Growth Serum Spray — Best premium

By far the biggest bottle here, and the only spray format in the group.

Best for: wanting the largest bottle and a spray-on scalp routine Skip it if: you want published dimensions and weight before buying

Moerie is the outlier on two counts. It's a spray, not a dropper serum, and at 5.07 fl oz it holds more than twice what any other pick here does. If you hate fiddling with drops, you spray it on the scalp after washing and leave it, which is the simplest routine of the five.

The ingredient pitch is broad. Moerie's listing claims 77 minerals, 18 proteins and 5 vitamins, with caffeine to block DHT and fulvic acid to funnel nutrients to each follicle. It also states you should start seeing results in 30 days, more at three months. Read those as manufacturer claims, not measured outcomes.

It's the priciest pick here. That's justified partly by the sheer size, but there's a real gap in the listing: no published weight and no dimensions, where every other serum gives you at least a bottle size and shape. If you want to know exactly what's arriving, the missing figures are frustrating. Buy this for volume of product and a fuss-free spray, not for spec transparency.

Pros:

• Largest bottle of the five at 5.07 fl oz
• Only spray format, simplest to apply
• Broad claimed mineral and protein content
• Caffeine listed as a DHT blocker

Cons:

• Most expensive pick here
• No published weight or dimensions
• Broad claims with no measured backing
• Spray may reach lengths you didn't target

5. Psalmonica Root Activator Serum — Best upgrade

A 1 fl oz botanical serum built to pair with a matching root shampoo.

Best for: pairing a serum with a matching root-activator shampoo for one routine Skip it if: you want a larger bottle than 1 fl oz

Psalmonica is the "upgrade" because it's designed as part of a system, not a standalone bottle. The listing points you to a companion Root Activator Shampoo and frames the two together as a complete root-strengthening routine. If you like your products to match, that's the appeal here.

The formula is the most botanical of the group. It blends rosemary oil, ginger root and black sesame, described as a concentrated scalp serum for thinning hair that works directly at the roots. Psalmonica calls it lightweight and fast-absorbing, non-greasy, and easy to layer with your regular products.

The catch is size. At 1 fl oz and 28.3 g, it's the smallest bottle in this roundup, half the size of The Ordinary or Marc Anthony. It sits in the middle of the price ladder, so you're paying a mid-tier price for the least product. That only makes sense if the botanical route and the shampoo pairing genuinely fit your plan. As a one-bottle purchase judged on milliliters, it's the weakest value here.

Pros:

• Botanical blend of rosemary, ginger, black sesame
• Designed to pair with a matching shampoo
• Listed as fast-absorbing and non-greasy
• Layers easily with other products

Cons:

• Smallest bottle at just 1 fl oz
• Mid-tier price for the least product
• Best value only if you buy the shampoo too
• Slowest seller of the five

Peptides, biotin or botanicals: which formula fits you?

The five picks split into three ingredient camps, and matching yours to your scalp saves you money.

1. Peptide-led. The Ordinary is the clear example, stacking REDENSYL, CAPIXYL and four more named complexes. This is the most cosmetic-science-heavy route and suits someone who wants density support over months.
2. Biotin and conditioning. Marc Anthony and Viviscal lean on biotin, with keratin and collagen in Viviscal's case. These target strand strength and a fuller look, often faster.
3. Botanical and mineral. Psalmonica's rosemary, ginger and sesame blend, plus Moerie's mineral-heavy spray, appeal if you prefer plant-forward or broad-spectrum formulas.

No camp is proven better by anything in these listings. Pick the one whose actives you'd actually want on your scalp daily, because consistency beats chemistry you'll abandon. If ingredient lists make your eyes glaze, the biotin group is the easiest to understand.

How long does one bottle last?

Bottle size is the least glamorous spec and the most useful. Here's the spread, largest to smallest:

• Moerie spray: 5.07 fl oz
• The Ordinary: 2.02 fl oz
• Marc Anthony: 2 fl oz
• Viviscal: 1.69 fl oz
• Psalmonica: 1 fl oz

A once-daily serum used a few drops at a time stretches further than a spray you mist across the scalp. So Moerie's size advantage shrinks in practice, because sprays use more per application. The Ordinary and Marc Anthony, at roughly 2 fl oz of dropper serum, likely last longest per use.

Psalmonica's 1 fl oz is the one to watch. It's fine as a trial or a companion to the shampoo, but if you're committing to a months-long routine, you'll reorder it soonest. Match bottle size to how patient your plan is: bigger bottles for the long game, smaller ones to test tolerance first.

When a different serum wins

The Ordinary is the default, but three specific situations flip that.

• If you want thickness for an event this week, Viviscal wins. Its listing is the only one claiming strands look thicker instantly, so it's the coating play rather than the slow follicle play.
• If your budget is the hard limit, Marc Anthony wins. It's the cheapest of the five at a full 2 fl oz, so you lose the least product to save the most money.
• If you want the biggest bottle or hate droppers, Moerie wins on format and sheer size at 5.07 fl oz, as long as you can accept its missing weight and dimension figures.

Everyone else should start with The Ordinary.

The verdict

If you want depth of formula and a serum to use for months, The Ordinary Multi-Peptide Serum for Hair Density is the pick. Six named peptide actives, a generous 2.02 fl oz bottle and a clean once-daily routine make it the most complete scalp treatment of the five. It's the fastest seller here too. That's the winner for most people reading this.

If your priority is spending the least, the answer changes. Marc Anthony Grow Long is the cheapest of the five and still gives you a full 2 fl oz, with biotin, caffeine and rosemary oil aimed at breakage as well as density. The exact cutoff is your tolerance for a shorter ingredient list: if six named peptides matter to you, pay up for The Ordinary; if biotin and caffeine at the lowest price are enough, Marc Anthony does the job for less.

Above both, remember the honest limit. None of these listings proves a volume result with a figure, so treat "volume" as what the formula targets. The best hair growth serum for volume is the one you'll apply every day without quitting, and The Ordinary's simple routine makes that easiest.

FAQ

Is a hair growth serum worth the money for volume?

A hair growth serum is worth it only if you use it consistently, because every formula here works over weeks or months rather than instantly. The exception is Viviscal, whose listing claims strands look thicker right away through coating. For long-term density support, The Ordinary's six named peptides give you the most formula for the price.

Is the best hair growth serum for volume actually proven to work?

The best hair growth serum for volume in this group isn't backed by any measured result in its listing. Brands describe supporting follicles or coating strands, but none publishes a density figure. Treat "volume" as the formula's stated goal, not a lab-confirmed outcome. Match the ingredient type to your scalp and judge results yourself over a few months.

How much serum is in each bottle here?

How much serum you get ranges widely across these five. Moerie holds the most at 5.07 fl oz as a spray. The Ordinary follows at 2.02 fl oz, Marc Anthony at 2 fl oz, Viviscal at 1.69 fl oz. Psalmonica is smallest at 1 fl oz. Dropper serums use less per application than sprays, so mid-size bottles often outlast the spray in practice.

The Ordinary versus Marc Anthony: which should I choose?

The Ordinary versus Marc Anthony comes down to formula versus price. The Ordinary lists six named peptide actives in a 2.02 fl oz bottle and sits in the pricier half. Marc Anthony matches the size at 2 fl oz, uses biotin and caffeine, and is the cheapest of the five. Pick The Ordinary for ingredient depth, Marc Anthony to save the most money.

What's the biggest mistake buying a volume serum?

The biggest mistake is buying for a same-day miracle and quitting early. Most serums here target follicles over months, so a week of use proves nothing. The second mistake is ignoring bottle size: Psalmonica's 1 fl oz empties fast on a long routine. Match your patience to the format, and expect coating serums like Viviscal to work faster than peptide ones.

Start with The Ordinary Multi-Peptide Serum for Hair Density. It gives you the deepest ingredient list of the five in a 2.02 fl oz bottle and asks only a few drops once a day, which is the routine you're most likely to keep. Consistency is what any of these formulas need, and the simplest habit wins. If price is your ceiling, drop to Marc Anthony without losing bottle size. Either way, judge volume by what you see over months, not by any label promise, since none of these serums proves the result with a number.

Last updated: September 13, 2026. Product availability re-checked.

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