Preguntas que la gente hace de verdad.

Un medidor de pantalla bien calibrado te lleva a unos ±0,4 de talla estadounidense cuando mides un anillo existente, y a unos ±0,65 cuando mides el dedo desnudo. El límite no está en las matemáticas, sino en la física. Con la densidad de pantalla habitual, un píxel de desalineación ya es alrededor de un quinto de talla, y una tarjeta un poco inclinada mide de menos. Mostramos el margen en cada resultado en lugar de dar un número pelado.

El navegador no tiene forma de saber el tamaño físico de tu pantalla. La misma imagen mide un número distinto de milímetros en un móvil, un portátil y un monitor 4K. Cualquier medidor que dibuje un círculo sin pedirte antes que calibres está adivinando, y una tabla impresa a la escala equivocada es peor que ninguna tabla.

Una moneda de tu propia divisa funciona bien: elige la tuya en la lista y usamos su diámetro publicado. También sirve una hoja A4 o Carta, doblada en cuatro si estás en el móvil. Puedes usar una regla, o dejar que rellenemos la escala según el modelo de tu dispositivo y confirmarla. Tener tarjeta no es universal, y un medidor que lo da por hecho no es realmente global.

Sí, y es una causa habitual de tallas equivocadas en otras webs. El zoom cambia el tamaño físico de un píxel CSS, así que una calibración hecha antes de ampliar ya no vale. Nuestro medidor detecta el cambio y te pide recalibrar en vez de darte en silencio un número incorrecto.

Miden cosas distintas. Una talla estadounidense es una posición en una escala que avanza exactamente 0,8128 mm de diámetro interior. Una talla británica es una letra en una escala que avanza 1,25 mm de circunferencia. Una talla ISO/UE es sencillamente la circunferencia interior en milímetros. Como los pasos difieren, las tallas enteras de un sistema rara vez caen en tallas enteras de otro: una 6 estadounidense es una L½ británica, no una letra redonda.

Coge prestado un anillo que ya lleve en el dedo correcto y mide su diámetro interior: es con diferencia lo más fiable. Si no puedes, presiona uno de sus anillos sobre una pastilla de jabón o plastilina para captar el borde interior, o traza el interior sobre papel. En último caso, compara su dedo con el tuyo y mide el tuyo. Las tallas adultas medias son 6–6,5 estadounidense en mujeres y 9–10 en hombres, pero tómatelo como último recurso, no como plan.

Normalmente sí. Un aro ancho abarca más dedo y aprieta más con el mismo diámetro interior. Por debajo de unos 4 mm no cambia nada en la práctica. A 6 mm sube un cuarto de talla; a 8–9 mm, alrededor de media. Nuestro medidor lo aplica por ti cuando indicas el ancho del aro, y funciona al revés con los interiores de confort, que quedan grandes.

Sube, en casi todos los casos. Un anillo algo holgado se puede reducir, acolchar o ajustar con bolitas. Un anillo que no pasa el nudillo es inservible, y forzarlo para sacarlo arriesga que se te quede atrapado el dedo. La excepción es un aro muy ancho o muy pesado, donde un ajuste holgado girará y se deslizará: ahí, mejor la talla más ceñida.

A última hora de la tarde o por la noche, a temperatura ambiente normal, cuando las manos no están ni frías ni hinchadas. Los dedos están más finos nada más levantarse y tras el frío, y más gruesos con calor, sal, ejercicio o un vuelo largo. Medir en tu media diaria da un anillo que sirve la mayor parte de las horas que estás despierto.

Normalmente sí. La mano dominante suele ser algo más grande, a menudo media talla. Mide el dedo exacto de la mano exacta en la que va a vivir el anillo, y recuerda que los dedos de la misma mano también difieren entre sí.

Las once principales: Estados Unidos y Canadá, el Reino Unido y los países Wheatsheaf, la Europa de la ISO 8653, Francia, Alemania y los Países Bajos, Rusia, Italia con España y Suiza, Brasil, Japón, China e India. Cada una se calcula a partir de la definición publicada de ese país en lugar de buscarla en una tabla, así que las conversiones son coherentes entre sí.

No. El cálculo se ejecuta por completo en tu navegador, y tu calibración se guarda solo en el almacenamiento local de tu propio dispositivo para que no tengas que repetirla. No hay cuenta, no hay subida y no hay nada que borrar por nuestro lado.

Solo si compruebas antes su escala. «Ajustar a la página» viene activado por defecto en muchos diálogos de impresión y reduce la hoja un pequeño porcentaje, suficiente para desplazar todas las tallas más de una talla entera. Nuestro medidor imprimible incluye un cuadrado de 50 mm para que lo midas antes de recortar nada.

Elige la talla con la que el anillo pase el nudillo y luego evita que gire en la base: bolitas de ajuste, un protector o un aro algo más pesado funcionan. Un joyero coloca las bolitas en minutos. Elegir la talla de la base significa un anillo que no te entra, que es el fallo peor.

US and Canadian sizes step in halves as standard, and in quarters for finer work — a quarter size is about 0.2 mm of inside diameter. UK sizes step in halves too, written as a letter and a half, like L½. Most mass-market retailers stock whole and half sizes only, so a quarter-size result is best read as a signal for which of the two neighbouring half sizes to order. Bespoke makers will work to a quarter size if you ask.

For a ring you cannot return — a wedding band, anything custom — get sized on a steel mandrel at a jeweller. They slide graduated steel rings onto the finger and read the fit directly, which takes screen calibration out of the equation entirely. It is free at most shops and takes two minutes. Use this tool to know what to expect before you walk in, to sanity-check the number you are given, and for everything you are buying online where a shop visit isn’t practical.

Give the size in their own system, and add the inside diameter in millimetres if there is a notes field. Retailers’ charts are not always identical — some round differently, and some list a “size 7” that is really an ISO 54 — so a millimetre figure removes the ambiguity. Check the returns policy on resizing before you order, and if the band is 6 mm wide or more, tell them the width so they can allow for it.

Lay an existing ring on a flat surface and measure straight across the inside, edge to edge through the centre — that is the inside diameter in millimetres. Finding the true centre line by eye is the hard part, and half a millimetre of error is already more than half a size, so take three readings at different angles and use the largest. If you have only the finger and no ring, wrap a paper strip round it and measure the strip instead: a ruler cannot read a curve.

Look inside the band first. Many rings are stamped with their size next to the metal mark — a number for US sizing, a letter for UK, sometimes a bare “54” for ISO. If the stamp is worn or absent, measure the inside diameter and convert. Be careful with second-hand and inherited rings: a ring that has been resized usually keeps its original stamp, so the number inside can be a size or two away from what it now measures.

With two tools. A ring stick, or mandrel, is a tapered steel cone marked with sizes — an existing ring slides down it until it stops, and the mark at that point is the size. A set of ring gauges is a keyring of graduated steel bands, tried on the finger one at a time until one fits. The mandrel measures rings; the gauges measure fingers. Both are physical standards, which is precisely what an online sizer is calibrating itself towards.

Four steps, about two minutes. One: calibrate the screen by matching the on-screen outline to a bank card, a coin or a sheet of paper. Two: choose whether you are measuring an existing ring or a bare finger. Three: adjust the on-screen circle or band until it matches, viewed square to the screen rather than at an angle — viewing angle is the single most common source of error. Four: read the result, which comes with a confidence range and the equivalent size in every major national system.

Yes — this page is that tool. There is nothing to install and no account to create: you calibrate the screen once against a known object, measure, and the conversion runs entirely in your browser. Expect roughly ±0.4 of a US size when measuring an existing ring and ±0.65 from a bare finger, which is close enough for most purchases and worth confirming at a jeweller for a wedding band. Your calibration is saved in your own device’s storage so you do not have to repeat it.

Yes, and a phone is how most people use this. Two phone-specific notes. First, if you are calibrating with paper, fold an A4 or Letter sheet in half twice so it fits the screen, and tell the sizer you have done so. Second, check that browser zoom is at 100% and that you are not in reader mode or a forced desktop-site view — both change the physical size of a CSS pixel and invalidate the calibration. Screen protectors are fine; a heavily cracked screen is not, so use the printable sizer in that case.

A properly calibrated screen sizer gets you to roughly ±0.4 of a US size when you measure an existing ring, and around ±0.65 when you measure a bare finger. The limit isn’t the maths — it’s physical. At a typical screen density one pixel of misalignment is already about a fifth of a size, and a card held slightly off the flat reads short. We show you the range on every result rather than printing a bare number.

A browser has no way of knowing the physical size of your display. The same image is a different number of millimetres on a phone, a laptop and a 4K monitor. Any sizer that draws a circle without asking you to calibrate first is guessing — and a chart printed at the wrong scale is worse than no chart.

A coin from your own currency works well — pick yours from the list and we use its published diameter. So does a sheet of A4 or US Letter, folded in half twice if you’re on a phone. You can also use a ruler, or let us pre-fill the scale from your device model and confirm it. Card ownership isn’t universal, and a sizer that assumes it isn’t really global.

Yes, and it’s a common cause of wrong sizes elsewhere. Zooming changes the physical size of a CSS pixel, so a calibration done before you zoomed is no longer valid. Our sizer watches for the change and tells you to recalibrate instead of silently handing you a wrong number.

They measure different things. A US size is a position on a scale that steps by exactly 0.8128 mm of inside diameter. A UK size is a letter on a scale that steps by 1.25 mm of circumference. An ISO/EU size simply is the inside circumference in millimetres. Because the steps differ, whole sizes in one system rarely land on whole sizes in another — a US 6 is a British L½, not a round letter.

Borrow a ring they already wear on the right finger and measure its inside diameter — that’s the most reliable route by a wide margin. If you can’t, press one of their rings into a bar of soap or plasticine to capture the inner edge, or trace round the inside on paper. Failing that, compare their finger to your own and measure yours. Average adult sizes are US 6–6.5 for women and US 9–10 for men, but treat that as a fallback, not a plan.

Usually, yes. A wide band contacts more of the finger and wears tighter at the same internal diameter. Below about 4 mm it makes no practical difference. At 6 mm go up about a quarter size; at 8–9 mm about half. Our sizer applies this for you when you set the band width — and it works in the other direction for comfort-fit interiors, which run large.

Go up, in almost every case. A slightly loose ring can be sized down, padded, or fitted with sizing beads. A ring that won’t clear your knuckle is unwearable, and forcing it off risks a trapped finger. The exception is a very wide or very heavy band, where a loose fit will spin and slide — there, favour the snugger size.

Late afternoon or evening, at normal room temperature, when your hands are neither cold nor swollen. Fingers are smallest first thing in the morning and after cold exposure, and largest after heat, salt, exercise or a long flight. Measuring at your daily average gives a ring that fits for most of your waking hours.

Usually. The dominant hand tends to be slightly larger, often by about half a size. Measure the exact finger on the exact hand the ring will live on — and remember that fingers on the same hand differ too.

All eleven of the major national standards: the United States and Canada, the UK and the Wheatsheaf countries, ISO 8653 Europe, France, Germany and the Netherlands, Russia, Italy and Spain and Switzerland, Brazil, Japan, China, and India. Every one is computed from that country’s published definition rather than looked up in a table, so the conversions stay internally consistent.

Your measurement isn’t. The calculation runs entirely in your browser, and your calibration is stored only in your own device’s local storage so you don’t have to redo it — there’s no account and no upload, and no size, finger measurement or calibration value ever reaches us. Like most sites we do count page views, using Google Analytics, which records that a page was opened and can’t see what you measured on it. The privacy policy sets out exactly what that collects and how to switch it off.

Only if you check its scale first. “Fit to page” is on by default in many print dialogs and quietly shrinks the sheet by a few percent, which is enough to shift every size on it by more than a full size. Our printable sizer includes a 50 mm square to measure before you cut anything out.

Size so the ring clears the knuckle, then stop it spinning at the base — sizing beads, a ring guard, or a slightly heavier band all work. A jeweller can fit beads in minutes. Sizing for the base instead means a ring you can’t get on, which is the worse failure.