# Text expansion in translation: why translated banners break

> Translated headlines can run two to three times longer than the English. See the W3C and IBM figures by string length and how to design banners with room.

By The BannerTranslate team. Published 2026-11-13.
Web page: https://bannertranslate.com/resources/text-expansion-in-translation

Translated text is almost never the same length as the original, and short strings swing the most. IBM's guidance, reproduced by the W3C, puts the average for an English string of up to 10 characters at 200–300% of its original length once it is translated into European languages, falling to 130% for strings over 70 characters. A banner headline or button label is exactly that kind of short string, sitting in a fixed space, which is why it is the first thing to break. This guide covers the figures, the cases where text gets shorter, wider or taller instead, and seven design habits that leave room.

## How much longer does translated text get?

The W3C Internationalization article *Text size in translation* makes two points that matter for banners. English is unusually compact, so text translated out of it typically comes out longer. And the growth is uneven: the shorter the source string, the larger the likely expansion.

The article reproduces average expansion rates for text translated from English into European languages, which it attributes to IBM's *Guidelines to design global solutions*. Here they are as the W3C gives them.

| Characters in the English source | Average expansion |
| --- | --- |
| Up to 10 | 200–300% |
| 11–20 | 180–200% |
| 21–30 | 160–180% |
| 31–50 | 140–160% |
| 51–70 | 151–170% |
| Over 70 | 130% |

Read the percentages as translated length relative to the original. The W3C calls an Italian word three times as long as its English source a 300% expansion, so 200% means twice as long.

These are averages across European languages, not a promise about any one string. The 51–70 row also breaks the downward pattern on the W3C page; I have reproduced it as published.

The W3C's worked example is the label Flickr used for photo views. Against the five-letter English word, the Korean came out at 0.8 times the length, the German at 2.8 and the Italian *visualizzazioni* at 3.

## Why short strings expand the most

Mostly it is arithmetic. In a two-word call to action, one longer word changes the total by half, while in a 40-word paragraph it disappears. Short English labels also lean on abbreviations that other languages spell out: the W3C notes that Flickr's "FAQ" became *Perguntas freqüentes* in Portuguese, which is 20 characters where English used 3.

The other half of the problem is where short strings live. The W3C observes that the smaller the English text, the more likely it has been squeezed into a small space, such as inside a graphic. On a banner, that means the button, the badge and the headline.

Here is an illustration with a common call to action. We chose these ordinary translations and counted them ourselves, spaces included. They are not sourced statistics, and a native copywriter might pick different wording.

| Language | "Shop now" | Characters | Against English |
| --- | --- | --- | --- |
| English | Shop now | 8 | 100% |
| Finnish | Osta nyt | 8 | 100% |
| Arabic | تسوق الآن | 9 | 113% |
| Italian | Acquista ora | 12 | 150% |
| Portuguese (Brazil) | Compre agora | 12 | 150% |
| Spanish | Comprar ahora | 13 | 163% |
| Russian | Купить сейчас | 13 | 163% |
| German | Jetzt einkaufen | 15 | 188% |
| French | Acheter maintenant | 18 | 225% |
| Chinese (Simplified) | 立即购买 | 4, or 8 at double width | 50%, or 100% |
| Japanese | 今すぐ購入 | 5, or 10 at double width | 63%, or 125% |
| Korean | 지금 구매하기 | 7, or 13 at double width | 88%, or 163% |

Even this friendly example reaches 225% in French, and most of my picks sit below IBM's 200–300% average for strings this short. Treat it as the gentle case.

Compound words add a twist. "Summer sale" is 11 characters in two words, while the German *Sommerschlussverkauf* (my example again) is 20 characters in one word that will not wrap. The W3C makes the same point about Finnish, German and Dutch, with "Input processing features" becoming *Eingabeverarbeitungsfunktionen*.

## When text gets shorter, wider or taller instead

**Shorter.** Translation can contract. A Finnish shop may say *Kesäale* for "Summer sale", which is 7 characters against 11 (my own example). The W3C warns that shorter translations can be as awkward as longer ones if they leave too much white space.

**Fewer characters, more width.** Chinese, Japanese and Korean often need fewer characters, but each one is wider. In its Flickr table the W3C counts each Chinese and Korean character as two English characters in width. Google does the same for ad copy: according to Google Ads Help, each character in a double-width language such as Korean, Japanese or Chinese counts as two towards a text ad's character limit.

**Taller.** Width is only half of the box. The W3C says many non-Latin scripts have taller characters and need more space between lines, and it lists Arabic (especially in Nastaliq fonts), Chinese, Devanagari (used for Hindi), Japanese, Korean and Tibetan among them. Its side-by-side graphic shows two lines of Thai taking around 150% of the vertical space of the same English text.

Google's Material Design guidance sorts scripts in a similar way. It classes Arabic, Hindi, Thai and Vietnamese as "tall" and Chinese, Japanese and Korean as "dense", and says both groups need extra line height. For Japanese book pages, the W3C's layout requirements describe a gap between lines of half to one full character size as common, which means lines pitched at 1.5 to 2 times the character size.

**Bigger at the small end.** Complex characters lose detail sooner as type shrinks. The W3C notes that Japanese authors may avoid bold and italic because the characters are too complicated to look good at small sizes with those effects. I could not find an authoritative universal minimum size, so test at real size instead of trusting a number.

## Seven design habits that leave room

1. **Give every text element a length budget.** Turn IBM's figures round: a headline of up to 10 characters should fill no more than a third to a half of its line in English (100 ÷ 300 and 100 ÷ 200), and one of 11–20 characters about half. Hard limits work the same way. Google Ads Help gives responsive display ads a short headline of 30 characters or fewer, so 15 English characters is about the ceiling if a 180–200% translation has to fit.
2. **Let buttons grow with their label.** Set the padding and let the width follow the words. Say your English "Shop now" measures 90 px on a 300×250 banner with 260 px of usable width: at 200–300% the label alone needs 180–270 px, so a button drawn 110 px wide was never going to survive.
3. **Keep words out of tight shapes.** Starbursts, ribbons and circles are drawn around one specific word. The W3C advises particular care when fitting text snugly into graphic designs, and a three-letter "NEW" badge is the snuggest fit there is.
4. **Design every headline to tolerate a second line.** A one-line headline with no vertical slack can only cope with growth by shrinking. Leave room for two lines, and check that the longest single word fits the line width alone, because compounds will not break.
5. **Do not let all-caps carry the hierarchy.** According to the Unicode Consortium, the vast majority of scripts have no case distinction; the widely used cased scripts are Latin, Greek, Armenian and Cyrillic. Apple adds that Arabic and Hebrew can look too small beside uppercased Latin text and suggests raising the right-to-left font size by about 2 points. Build emphasis from size, weight and colour instead.
6. **Set a minimum type size and treat it as a floor.** Decide the smallest size you will accept on the smallest placement, such as a 320×100 large mobile banner, and check each language there at 100% zoom. If a translation only fits below the floor, the copy is too long.
7. **Leave vertical slack for taller scripts.** On a 728×90 leaderboard, two lines of 28 px type at a line height of 1.2 take about 67 px. Scale that by the roughly 150% the W3C's Thai example needed and you reach about 101 px, which is taller than the banner.

If you [translate a banner](https://bannertranslate.com/app) with BannerTranslate, each version keeps the banner's own pixel size and layout and only the words change. The room you left in the original is therefore the room the translation gets, so these habits matter before you upload.

## What to do when the translation still does not fit

Work through these in order. The first one fixes most cases.

1. **Shorten the copy with a native writer.** Ask for the same message in fewer words, with a character target taken from your budget. A good writer will find a shorter idiom; a font slider will only find a smaller size.
2. **Use the second line** you left room for, breaking at a phrase boundary chosen by someone who reads the language.
3. **Trim the supporting text first.** If something has to go, drop the subline before you squeeze the headline or the call to action.
4. **Reduce the size last, and not below your floor.** Check the result on the smallest placement before accepting it.
5. **Do not abbreviate or distort.** The W3C advises thinking twice about abbreviations, because other languages may not be able to replicate them. Do not squash the letters horizontally either, and never adjust letter spacing in Arabic script, where MDN notes that letters are expected to stay visually connected.

Then go back and fix the source design, because the next campaign will hit the same wall. The [banner localization guide](https://bannertranslate.com/resources/banner-localization-guide) covers what else changes besides the words, and [right-to-left banner design](https://bannertranslate.com/resources/right-to-left-banner-design) covers Arabic, Hebrew, Persian and Urdu.

## A pre-flight checklist before you translate

Run this on the source banner before any translation starts.

- The headline fills no more than about half of its line in English.
- The headline area can take two lines at a more generous line height than your Latin setting.
- The longest word you can imagine in German or Finnish would fit the line width alone.
- Buttons are built as padding around text, with spare width on both sides.
- No translatable word sits inside a shape drawn to fit it.
- Nothing depends on capital letters or italics for emphasis.
- The smallest text is readable at 100% on your smallest placement.
- Abbreviations are spelled out, or listed with their meanings for the translator.
- Someone who reads each target language is lined up to review the result.

If you are producing many sizes as well as many languages, test the tightest one first. Our guides to [Google Display ad sizes](https://bannertranslate.com/resources/google-display-ad-sizes) and to [running a multilingual banner campaign](https://bannertranslate.com/resources/multilingual-ad-campaign-workflow) show which placements are least forgiving and where review fits, and the [resources](https://bannertranslate.com/resources) hub has the rest.

## FAQ

### How much does text expand when translated from English?

It depends mainly on how long the source is. IBM's averages for European languages, as reproduced by the W3C, run from 200–300% of the original length for strings of up to 10 characters down to 130% for strings over 70 characters. Individual strings can land well outside those averages.

### Which languages expand the most?

There is no reliable single percentage per language, and I have deliberately not given one. In the W3C's one-word Flickr example, Italian came out at 3 times the English and German at 2.8 times, but another word could reverse the order. Plan by string length, then check the real translation.

### Does text ever get shorter in translation?

Yes. In the same W3C example the Korean was 0.8 times the English, and Chinese, Japanese and Korean often use fewer characters overall. Fewer characters does not mean less space, because those characters are wider and usually need more line height.

### Should I shrink the font to make a translation fit?

Only as a last resort, and never below the minimum you set for the smallest placement. Shrinking hides the real problem, which is copy that is too long for the space. Ask a native writer for a shorter version first.

### How much extra room should a button have?

A button label is usually under 10 characters, which puts it in IBM's 200–300% band. A sensible target is a button whose label can double in width, with the layout still working if it triples.

### Does a translation tool solve text expansion for me?

No tool removes the underlying constraint, which is the space in your design. With BannerTranslate you upload one banner and choose up to 5 of 46 languages, and each result is a flat image at the original pixel size, not editable layers. It is drawn by an AI image model, so someone who reads the language should check every version before it is published; [how to translate a banner](https://bannertranslate.com/resources/how-to-translate-a-banner) covers the steps.

## Sources

- [W3C Internationalization, Text size in translation](https://www.w3.org/International/articles/article-text-size) – the IBM expansion table by string length, the Flickr example, compound nouns, character width, line height and abbreviations.
- [W3C, Requirements for Japanese Text Layout](https://www.w3.org/TR/jlreq/) – the common line gap of half to one character size for Japanese book pages.
- [W3C Internationalization, Using b and i elements](https://www.w3.org/International/questions/qa-b-and-i-tags) – Japanese characters being too complicated for bold and italic at small sizes.
- [Material Design, Language support](https://m2.material.io/design/typography/language-support.html) – the English-like, tall and dense script categories and their extra line height.
- [Unicode Consortium, FAQ on character properties, case mappings and names](https://www.unicode.org/faq/casemap_charprop.html) – which scripts have upper and lower case.
- [Apple Human Interface Guidelines, Right to left](https://developer.apple.com/design/human-interface-guidelines/right-to-left) – balancing Arabic and Hebrew against uppercased Latin text.
- [Google Ads Help, Create a responsive display ad](https://support.google.com/google-ads/answer/7005917) – the 30-character short headline limit.
- [Google Ads Help, About text ads](https://support.google.com/google-ads/answer/1704389) – double-width characters counting as two towards a limit.
- [MDN Web Docs, letter-spacing](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/letter-spacing) – why Arabic script should not have letter spacing applied.