How Yomite reads numbers, units and dates aloud

Yomite turns numbers, units and dates into the way a person would say them before it reads them aloud: “2024/12/31” is read as a date, “100kg” as “100 kilograms” and “¥1,000” as “1,000 yen”. A dictionary-based preprocessing layer does this automatically, so there is nothing to set up.

Related use case: Content creators

“100kg” read out as “hyaku kē jī.” A date like “2024/12/31” spelled out digit by digit — “two-zero-two-four slash one-two slash three-one.” “H₂O” trailing off after just “H.”

If you’ve used a system TTS voice or a generic cloud TTS engine, you’ve probably run into this. Text with numbers, units, and symbols mixed in is a minefield for most speech synthesis.

Yomite solves this with a dictionary-based preprocessing layer. Before any text reaches the synthesis engine, it normalizes dates, times, currency, SI units, math operators, chemical formulas, Roman numerals, fractions, and Greek letters into the way a person would actually say them out loud.

Which notations does Yomite read correctly?

Yomite’s site publishes a comparison table with real conversion examples. Here’s a slice of it:

Input text	Other TTS (system / generic cloud)	Yomite
2024/12/31	”two-zero-two-four…"	"December 31, 2024” (read naturally)
12:30	”one-two colon three-zero"	"12:30” (read as a time)
100kg / 3.5m² / 30°C	”hyaku kē jī” / skipped	”100 kilograms / 3.5 square meters / 30 degrees”
¥1,000 / $50	”one-zero-zero-zero” (symbol skipped)	“1,000 yen / 50 dollars”
3 + 4 = 7	”three four seven” (operators ignored)	“3 plus 4 equals 7”
H₂O / CO₂	”H” / “C-O” only	”H-two-O” / “C-O-two”
½ / ¾	often skipped entirely	”one half” / “three quarters”
α, β, γ	misread, not recognized as Greek letters	”alpha, beta, gamma”

The categories covered fall into eight groups:

• Dates & times (YYYY/MM/DD, HH:MM:SS)
• SI units (kg, km, Hz, °C, m², kWh…)
• Currency (¥, $, €, £)
• Math operators & symbols (+, −, ×, ÷, ±, =, ≠, %, ‰)
• Chemical formulas (H₂O, CO₂, NaCl)
• Roman numerals (Ⅰ–Ⅻ)
• Greek letters (α, β, γ … ω)
• A standard dictionary of 5,000+ entries covering commonly mispronounced words and web-novel/light-novel proper nouns

These conversions are continuously verified by automated tests and applied automatically every time text is loaded — there’s no setup required on your end.

Do I need to set anything up?

Yomite has a separate feature: a per-book pronunciation dictionary where you register custom readings for things like invented fantasy names that don’t exist in any dictionary.

Number, unit, and symbol normalization is a different kind of problem. How “100kg” should be read isn’t something that varies by book — it has one correct reading in natural speech. That’s why Yomite builds this in as a standard, always-on layer rather than something you configure. It applies the moment text is imported, with nothing for you to set up.

Where does it make a difference?

Normalization pays off most outside of fiction, wherever numbers and symbols carry real information:

• Papers and technical documents — when you listen to PDFs and papers, chemical formulas, units, and equations show up constantly. If “H₂O” or “100GB” gets mangled every time, comprehension suffers.
• Business documents and reports — dates, timestamps, amounts, and percentages need to come through correctly the first time, or you end up rewinding to catch the number you missed.
• News and web articles — statistics, prices, and temperatures are often the actual point of the sentence.
• Recipes and how-to guides — measurements (½ cup, 100g, 30°C) are everywhere in this genre, and a skipped unit changes the meaning of the instruction.

The takeaway

Getting distracted by “hyaku kē jī” instead of the content itself is a small thing that adds up to a real dent in immersion. Yomite normalizes dates, times, units, currency, math, chemical formulas, Roman numerals, Greek letters, and a 5,000+ entry standard dictionary automatically, through a dictionary-based preprocessing layer — no setup required. Import your text and it reads naturally from the first sentence.

If you regularly listen to text full of numbers and symbols, the difference is audible immediately.

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Get 読み手 Yomite on the App Store

Related: Fixing TTS mispronunciations with the pronunciation dictionary · Listening to papers and PDFs · Aozora Bunko read aloud: a step-by-step guide

Questions or feedback: [email protected]

— Yomite Team

Related guides

• Fixing misreadings with the pronunciation dictionary
• Proofreading your writing by ear