Do Thinx and Aisle use the same absorbency labels?

No. Thinx publishes 3 current tiers (108 mL across the range) and Aisle publishes 4 (5–40 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 Thinx and Aisle sizes compare?

Thinx runs true to size; Aisle tends to run small (many people size up). 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.

Is Thinx or Aisle better?

Neither is better across the board - they differ on measurable things. Compare three numbers on this page: the millilitres at the tier you actually need (not the tier names), how each brand's sizing runs for your hip measurement, and current prices in the catalog. The right brand is the one whose numbers fit your flow and your body, and that answer differs by person.

Thinx vs. Aisle

How Thinx and Aisle 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, Thinx reaches a higher maximum capacity (up to 108 mL) than Aisle (up to 40 mL) at its highest current tier. That does not make every Thinx pair more absorbent than every Aisle pair - it means the top of Thinx's range is higher. Compare tier by tier in millilitres, not by the label words.

Absorbency tiers, side by side

Thinx

See Thinx

Tier	Capacity	Grade
All Day	108 mL	Data quality grade B, converted from tampon counts
All Night	108 mL	Data quality grade B, converted from tampon counts
Overnight (Teens)	108 mL	Data quality grade B, converted from tampon counts

Verified against Thinx's own pages 2026-09-05

Aisle

See Aisle

Tier	Capacity	Grade
Essential Thong (Light)	5 mL	Data quality grade B, converted from tampon counts
Essential Brief/Hipster/Boxer (Moderate)	20 mL	Data quality grade A, brand publishes mL
BOOST (adjustable, +BOOSTER insert)	20–40 mL	Data quality grade B, converted from tampon counts
Super (Heavy / overnight)	40 mL	Data quality grade A, brand publishes mL

Verified against Aisle'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 under 3 mL each, 2 mL on average, before leaking - far below these maximums. Use the numbers to compare the two brands like for like, not as a leak-free guarantee.

Sizing

Thinx runs true to size; Aisle tends to run small (many people size up). 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.

Thinx: Runs true to size. Thinx states styles are "completely true to size" and recommends following the HIP measurement (measured at widest point, derriere included) for the most accurat

Aisle: Brief & Hipster: "Between sizes? We recommend sizing up." Between XL and 1X, the 1X is roomier through the waist. Thongs run LARGE in sizes 1X and 2X, so Aisle recommends sizing DO

Quick answers

Is Thinx or Aisle more absorbent?: By their own published claims, Thinx reaches a higher maximum capacity (up to 108 mL) than Aisle (up to 40 mL) at its highest current tier. That does not make every Thinx pair more absorbent than every Aisle pair - it means the top of Thinx'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 Thinx and Aisle use the same absorbency labels?: No. Thinx publishes 3 current tiers (108 mL across the range) and Aisle publishes 4 (5–40 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 Thinx and Aisle sizes compare?: Thinx runs true to size; Aisle tends to run small (many people size up). 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.
Is Thinx or Aisle better?: Neither is better across the board - they differ on measurable things. Compare three numbers on this page: the millilitres at the tier you actually need (not the tier names), how each brand's sizing runs for your hip measurement, and current prices in the catalog. The right brand is the one whose numbers fit your flow and your body, and that answer differs by person.

Skip the comparison - get your answer

Tell the translator your flow and it gives the covering tier at both Thinx and Aisle. Tell the size finder your hip and it gives your size in each.

What absorbency do I need?Find my size