The iron symbol and its heat dots
A plain iron is permission to press. The dots inside it are the ceiling — and your iron’s dial spells that ceiling out in fabrics instead of dots.
Iron, any temperature: Ironing is fine at any temperature, with or without steam.
Iron, low heat: Iron on low — up to about 110°C — for acetate, acrylic, and nylon.
Iron, medium heat: Iron on medium — up to about 150°C — for wool, silk, and polyester blends.
Iron, high heat: Iron on high — up to about 200°C — for cotton and linen.
What the iron symbol looks like
The mark is a clothes iron seen from the side: flat soleplate along the bottom, pointed nose, a handle arching over the top. On its own, with nothing inside and nothing underneath, it means ironing is fine at any temperature, with or without steam — the fabric will take whatever your iron does.
Every other mark in this family is that same iron with something added. Dots inside set a heat ceiling. Crossed-out steam lines underneath mean press it dry. An X across the whole shape means don’t press it at all.
One dot, two dots, three dots
One dot is low heat, up to about 110°C (230°F). That is the acetate, acrylic, and nylon end of the closet — fabrics that don’t so much scorch as melt. Two dots is medium, up to about 150°C (300°F): wool, silk, and polyester blends. Three dots is high, up to about 200°C (390°F), for cotton and linen, the only fabrics that genuinely need that much heat to go flat.
The dot count is a ceiling, not a target. Pressing a three-dot cotton shirt on the medium setting is always within the tag — it just takes more passes and leaves a little more crease behind. Going the other way is where garments are lost.
Your iron’s dial names fabrics, not dots
Here is the gap nobody warns you about: tags speak in dots, irons speak in fabrics. Almost every dial reads something like “synthetic — silk/wool — cotton/linen,” sometimes with nylon or rayon squeezed in at the cool end. Read them in the same order as the dots: one dot is the synthetic setting, two dots is the silk/wool setting, three dots is cotton/linen.
Dials are not precise instruments, though. They run warm or cool from one iron to the next, and the marked temperature is what the soleplate aims for, not what the fabric feels under it. Where the dial wording and the tag disagree, take the cooler reading, and test on an inside seam or a hem allowance before you touch the front of the garment.
What too much heat actually does
On synthetics, too hot is not a scorch mark, it is a change of state: acetate and acrylic glaze over, go shiny, and in the worst case stick to the soleplate and pull away with it. That shine does not wash out. Wool and silk scorch instead — a yellow-brown press mark, usually on a collar or a cuff, and usually there before you smell anything.
Going too cool costs nothing but time and a few wrinkles that stay in. So when you can’t tell how many dots the tag shows, start at the bottom of the dial, put a pressing cloth between the iron and the fabric — an old cotton pillowcase does the job — and step up one setting at a time.
Questions people actually ask
What temperature is two dots on an iron?
Medium heat, up to about 150°C — roughly 300°F. On an iron whose dial names fabrics rather than dots, that is the silk/wool setting, and it covers most polyester blends as well.
Can I iron a three-dot garment on a lower setting?
Yes. The dots are a maximum, not an instruction. A cooler iron on cotton or linen simply takes more passes, and a damp pressing cloth makes up much of the difference.
Related
Reading a whole tag, not one symbol? Tap everything you see into the decoder — it gives the careful combined plan.