Knix vs. Ruby Love

How Knix and Ruby Love period underwear compare on the only thing that travels across brands - capacity in millilitres - plus how each one's sizing runs. No brand's thumb on the scale.

Updated 2026-06-12 · Every capacity is the brand's own claim, graded and dated

By their own published claims, Knix reaches a higher maximum capacity (up to 99 mL) than Ruby Love (up to 12.5 mL) at its highest current tier. That does not make every Knix pair more absorbent than every Ruby Love pair - it means the top of Knix's range is higher. Compare tier by tier in millilitres, not by the label words.

Absorbency tiers, side by side

TierCapacityGrade
Light5–15 mLData quality grade B, converted from tampon counts
Moderate18–36 mLData quality grade C, conflicting / unconfirmed claim
Heavy36–63 mLData quality grade C, conflicting / unconfirmed claim
Ultra63–99 mLData quality grade C, conflicting / unconfirmed claim

Verified against Knix's own pages 2026-06-11

Ruby Love

See Ruby Love
TierCapacityGrade
Period underwear (one level)12.5 mLData quality grade B, converted from tampon counts

Verified against Ruby Love's own pages 2026-06-05

Claims, not lab measurements

Every capacity above is the brand's own maximum claim, typically from a saline saturation test. The only published study with real blood components (BMJ Sexual & Reproductive Health, 2023) measured period underwear holding about 1 to 3 mL before leaking - far below these maximums. Use the numbers to compare the two brands like for like, not as a leak-free guarantee.

Sizing

Knix tends to run small (many people size up); Ruby Love runs true to size. Both brands size from your hip measurement, so rather than converting one brand's size into the other's, the size finder gives you your size in each directly.

Knix: Brand labels core styles "True to Size" on product pages (e.g. Essential High Rise). However, customer reviews consistently report the leakproof styles run small / recommend sizing

Ruby Love: Ambiguous in brand materials. The sizing guide and FAQ say buy "True to size for best fit" and that underwear "should fit comfortably snug for maximum leak-proof performance." Howe

Quick answers

Is Knix or Ruby Love more absorbent?
By their own published claims, Knix reaches a higher maximum capacity (up to 99 mL) than Ruby Love (up to 12.5 mL) at its highest current tier. That does not make every Knix pair more absorbent than every Ruby Love pair - it means the top of Knix's range is higher. Compare tier by tier in millilitres, not by the label words. And remember these are saline-lab maximums, not leak-free guarantees - the only blood-component study measured far lower real capacity.
Do Knix and Ruby Love use the same absorbency labels?
No. Knix publishes 4 current tiers (15–99 mL across the range) and Ruby Love publishes 1 (12.5 mL). Even where the words overlap, the millilitres differ, which is exactly why this page compares them in millilitres with a data-quality grade on every number.
How do Knix and Ruby Love sizes compare?
Knix tends to run small (many people size up); Ruby Love runs true to size. Both size from your hip measurement, so the size finder gives your size in each brand directly rather than guessing from the other brand's number.

Skip the comparison - get your answer

Tell the translator your flow and it gives the covering tier at both Knix and Ruby Love. Tell the size finder your hip and it gives your size in each.