ISO 3758 / ASTM D5489
What the signs
on your clothes
actually mean
There are only five shapes and three modifiers. Once you know how they combine, you can read a care label from any country without looking anything up again.
A typical label — tap a symbol
The grammar
Tub is washing. Triangle is bleaching. Square is drying. Iron is ironing. Circle is professional cleaning. Always in that order, left to right.
More dots, more heat. One dot is the coolest setting the machine offers, three is the hottest. European labels often print a number instead.
Bars underneath have nothing to do with temperature. One bar means reduced agitation and spin. Two bars means the wool or delicates programme.
An X over any symbol cancels that process entirely. This is the one modifier that is never a suggestion.
The wash tub
Everything about water: whether the garment can be washed at all, how hot, and how roughly the machine is allowed to treat it.
Machine wash
No restriction stated. Any normal cycle is fine, but if no temperature is given, 40 °C is the sensible default.
Maximum 30 °C
A cool wash. Common on dark colours, prints and anything with elastane. Cool water is also what keeps black jeans black.
Maximum 40 °C
The everyday setting. Handles most cottons, mixed loads and everyday synthetics without shrinking them.
Maximum 60 °C
Hot enough to deal with bacteria and dust mites. This is the setting for bed linen, towels and cleaning cloths.
Maximum 95 °C
A boil wash, now rare. Reserved for white cotton and household textiles that need to be sanitised.
Mild cycle
One bar: the machine must reduce agitation and spin speed. Look for “easy care”, “synthetics” or “permanent press” on the dial.
Very mild cycle
Two bars: barely any movement, minimal spin, generous water. On most machines this is the wool or hand-wash programme.
Hand wash only
Maximum 40 °C, by hand. Move the garment gently through the water and press the water out — never twist or wring it.
Dots instead of a number
North American labels use dots for temperature: one = 30 °C, two = 40, three = 50, four = 60, five = 70, six = 95.
Do not wash
Water will damage this garment. Check the circle symbol — it almost always means professional cleaning instead.
The triangle
Only three variations exist, and on most modern labels you will only ever meet the crossed-out one.
Any bleach allowed
Including chlorine bleach. Almost only seen on white cotton and household linen. Dilute it properly regardless.
Oxygen bleach only
Two diagonal strokes: non-chlorine bleach. This is the “colour-safe” kind, and the active ingredient in most stain removers.
Do not bleach
Also rules out detergents containing bleach. Check the box before you pour — many “whitening” powders count.
Older label: CL
A triangle containing the letters CL is the pre-2012 way of saying chlorine bleach is permitted. Treat it as the empty triangle.
The square
A circle inside the square means a tumble dryer. Lines inside the square mean air drying, and the direction of the lines tells you how to hang it.
Tumble dry
Safe for the dryer, no heat limit stated. Even so, the dryer is the single biggest cause of shrinkage and pilling.
Low heat
One dot, roughly 60 °C at the exhaust. The setting usually labelled “delicate” or “low”.
Normal heat
Two dots, roughly 80 °C. The standard cotton programme on almost every dryer.
No heat
A filled circle means tumble without heat — the “air fluff” setting. It moves the garment but never warms it.
Tumble dry, mild
Bars work the same way here as on the wash tub: one bar reduces the mechanical action, two bars reduce it further.
Do not tumble dry
Air dry only. Look at the next symbol on the label to find out whether to hang it or lay it flat.
Line dry
One vertical line: hang it up, on a hanger or a washing line, after a normal spin.
Drip line dry
Two vertical lines: hang it soaking wet, without spinning or wringing. The weight of the water pulls the creases out.
Dry flat
One horizontal line: lay it on a towel and reshape it while damp. This is what saves knitwear from stretching out of shape.
Drip flat dry
Two horizontal lines: lay it flat without spinning it first. Heavy wool and cashmere usually ask for this.
Dry in the shade
A diagonal stroke in the top-left corner can be added to any of the four drying symbols. Direct sun will fade or yellow this fabric.
The iron
Dots here map onto real soleplate temperatures, and the gap between one dot and three dots is the difference between a pressed shirt and a melted one.
Maximum 110 °C
Low, and without steam. Acrylic, nylon, acetate and anything with elastane. Use a cloth between the iron and the fabric.
Maximum 150 °C
Medium. Polyester, viscose, wool and silk blends. On most irons this is the middle notch, often marked with the fabric names.
Maximum 200 °C
Hot, steam welcome. Cotton and linen. Linen in particular only presses properly when it is damp and the iron is hot.
Do not iron
Heat will glaze, melt or flatten this fabric permanently. Hang it in a steamy bathroom instead and let the creases drop.
Do not steam
The iron itself is allowed, the steam is not. Water marks this fabric — silk and some wools react this way.
The circle
This one is not addressed to you. The letter inside tells the cleaner which solvent to use, and the bars tell them how carefully.
Dry clean — P
Tetrachloroethylene, the standard solvent in most high-street shops. Normal process. Just hand it over.
Dry clean — P, mild
Same solvent, gentler handling: less mechanical action, lower temperature, shorter drying.
Dry clean — F
Hydrocarbon solvents only. Milder than P, and not every shop offers it, so mention it when you drop the item off.
Professional wet clean
Water-based, but done on specialist machines with controlled agitation. Not the same as washing it at home.
Wet clean — very mild
Two bars under the circle: the most cautious wet-cleaning programme available.
Do not dry clean
Solvents will damage the trims, the glue or the fabric itself. Common on garments with sequins, coatings or bonded seams.
Quick answers
The label has worn away completely. What now?
Wash at 30 °C on the gentle cycle, do not tumble dry, and iron on the lowest setting that does anything. That combination is too cautious for almost every garment, which is exactly why it will not ruin one.
Why does my label have dots where the guide shows numbers?
Two standards are in circulation. ISO 3758 is used across Europe and much of the world and prints the temperature as a number. ASTM D5489, used in the United States and Canada, prints dots instead. The shapes are the same in both — the two systems diverge in only three places.
| Dots | Temperature |
|---|---|
| 1 | 30 °C / 85 °F |
| 2 | 40 °C / 105 °F |
| 3 | 50 °C / 120 °F |
| 4 | 60 °C / 140 °F |
| 5 | 70 °C / 160 °F |
| 6 | 95 °C / 200 °F |
A symbol is missing from my label. Does that mean anything goes?
Technically the standard only requires the four domestic symbols, and a missing fifth symbol means no professional treatment is specified. In practice manufacturers print what matters, so a missing symbol is an absence of information rather than permission. Default to the gentler option.
What is the difference between “do not wash” and “dry clean only”?
“Do not wash” is a prohibition and nothing more — it rules out water at home. The circle symbol is the positive instruction that tells a professional what to do. A garment can carry a crossed-out tub and a crossed-out circle at the same time, which usually means surface cleaning only.
Do the bars mean the water is cooler?
No, and this is the most common misreading on a care label. Bars control how violently the drum moves, not how hot the water is. A tub marked 60 °C with two bars still wants 60 °C water — it just wants it delivered gently.
Are these symbols the same everywhere?
The five base shapes are near-universal. The differences are in the details: North America uses dots for washing temperature and a curved clothesline stroke for line drying, Japan adopted a system closely aligned with ISO in 2016, and older European garments may still carry the letters CL or A inside their triangles and circles. The full comparison is here.
Guides
Longer pieces on the things the symbols only hint at.
The three-hour wash that costs less than the thirty-minute one
Why the eco programme uses less electricity despite running for four hours, what each temperature is actually for, and what switching to 30 °C is really worth in money. With the arithmetic shown.
Nobody ever checked whether it washes
A dry clean only label is not a finding that washing fails — the rules require a manufacturer to certify one method and no more. What the tag is really protecting, which garments survive careful hand washing, and the one where the label is telling the truth.
The number on the dial is a programme name, not a temperature
Eco 40-60 is defined in European law by what it achieves rather than how hot it gets, most machines never reach 60 °C on a 60 °C wash, and your delicates cycle holds a fifth of what cottons does. How to translate a care label into the button in front of you.
Wool does not shrink. It ratchets.
The scales on a wool fibre act as one-way barbs, which is why felting cannot be undone. Why biological detergent quietly eats knitwear over months, what the superwash treatment actually does to the fibre, and why cashmere pills whatever you paid for it.
Shrinking, creasing and ironing are the same thing happening three times
All of it is one mechanism: water breaks the hydrogen bonds holding cellulose in shape, and they reform wherever the fabric is lying. Why cotton shrinks once and then stops, what pre-shrunk actually means, and why ironing dry linen achieves nothing.
A drop of water marks silk. A full wash does not.
Silk has no scales, so it cannot felt and agitation is not the danger. What actually destroys it is chemistry — attacked from both ends of the pH scale, degraded by daylight, and quietly wrecked under the arm by aluminium antiperspirant.
The thing that would clean your running shirt is the thing that would ruin it
Polyester absorbs around ten times more skin oil than cotton and spreads it where bacteria can reach it. Shifting oil takes heat, and heat destroys the elastane blended into almost everything. Why fabric softener makes both problems worse, and what shedding really depends on.
Not washing your jeans does not save the indigo
Indigo sits in a ring on the outside of the yarn and never bonds to it, so fading is unavoidable — you are only choosing whether it lands at the knees or everywhere. What the one real hygiene study found, why the freezer trick does nothing, and why stretch denim reverses all of it.
The smallest number on the label sets the rules
The other label — the one that is actually required by law. Why 5% elastane governs a 95% cotton garment, what “100%” legally allows on each side of the Atlantic, and the gap between a recycled claim that means 5% and one that means 50%.
The same five shapes, and exactly three differences
ISO 3758 and ASTM D5489 are close relatives, and most guides blend them into one confusing chart. Where they actually diverge, why two dots means 40 °C in a wash tub and 150 °C on an iron, and when Japan joined the system.
Five categories, not forty stains
The chemistry decides the treatment, not the alphabet. Why tipping salt on spilled red wine sets the stain instead of lifting it, why soap ruins a coffee mark, why you remove the greasy part of a combination stain first, and the one rule that never bends.
The wash is the easy part. The rinse is where it goes wrong.
Your hands cannot do what a drum does, so the washing barely needs technique. The arithmetic of the rinse, though, is worth knowing — pressing the water out between changes matters roughly fourteen times more than how many times you rinse.