How to write for HSE digital services - Numbers, measurements, dates and times

Numbers

Numerals (1, 2, 3 and so on)

We use numerals for all numbers (including 1 to 9). People generally find numerals easier to read and they scan for them.

For numbers over 999, use a comma for clarity. For example, 1,000.

For numbers less than 1, use 0 before the decimal point. For example, 0.25.

Exceptions:

  • use the numeral unless writing out the number makes more sense
  • write out numbers in common phrases where it would be odd to use a numeral (like 'one or two people' or 'one in a million')
  • write out numbers if 2 sets of numerals are next to each other - for example, in dosage
  • some further use cases of one

Examples of where we use numerals:

  • 1 to 2 teaspoons of honey
  • It takes 1 to 3 weeks from the time you were exposed to chickenpox for the spots to start appearing
  • Do this for 1 or 2 minutes
  • Depression affects about 1 in 10 people at some point during their life
  • 1-to-1 therapy

One or 1

We spell out 'one' when it means 'a' or to avoid repeating a word.

Examples:

  • Never take 2 doses at the same time to make up for a forgotten one
  • You can also phone 0818 22 44 78 to order one

We also use 'one' at the beginning of a sentence and in phrases like:

  • 'one or the other'
  • 'one of the most common'
  • 'one at a time'
At the start of a sentence

Never use '1' at the start of a sentence. But it is OK to use other numerals at the start of a sentence. If it looks confusing, consider rewording your sentence or writing out the number.

Ordinal numbers (1st, 2nd, 3rd and so on)

For numbers 1 to 9, we do not use ordinal numbers with letter suffixes. For example, '1st', as in 'your 1st vaccine'. Instead, spell out the word 'first'. This works better in page titles, headings and menu links.

For numbers 10 and higher, use ordinal numbers. These are easier to read as ordinal numbers with letter suffixes. For example, use '10th' not 'tenth', '50th' not 'fiftieth'.

Fractions and percentages

Spell out common fractions, such as two-thirds.

For percentages, use the % symbol. For example, 50%.

However, it's often better not to use a percentage. Instead of 50%, for example, you could say '1 in 2' or 'half'.

Do not mix fractions and percentages in one page, use one or the other.

Years and months

For anything over a year, use years and months, not just months.

For most audiences, writing the year followed by the month is most comprehensible.

✅ Good example:

  • 1 year and 6 months

❌ Bad examples:

  • 18 months
  • a year and a half
  • 1.5 years

Below a year

For anything below a year, use months.

✅ Good example:

  • 6 months old

❌ Bad examples:

  • half a year
  • 0.5 years
  • Ranges of years
  • For ranges of years, follow this format: 2 years to 2 years and 6 months

Measurements

Metric and imperial

We generally use metric.

It's sometimes helpful to use imperial. For example, for advice on cutting back on alcohol - 'Half a pint of beer is 1 standard drink.'

Do not use imperial for medicines dosage or infant feeding.

Weight

We say:

  • kg - not kilogram
  • g - not gram
  • mg - not milligram
  • microgram - not mcg

For the abbreviations, use lower case with no space. For example, 6g, 7kg and 10mg.

Calories

We use 'calorie' when talking about calories in general. For example, calorie information on menus. If needed, we can explain that calories are often written as kcal.

Distance

We say km, and not kilometre.

Do not use a space. For example, 'The Glencairn Medical Centre is 16km away.'

Length

For lengths, use:

  • cm - for centimetre
  • m - for metre
  • mm - for millimetre

Do not use a space. For example, 'A 45cm exercise ball is suitable for most people'.

Data storage units

Use upper case with a space. For example, 300 KB and 999 MB.

Dosage

We do not use a space between amount and measurement.

Use your judgement when explaining medicines doses. Avoid having 2 sets of numerals next to each other. Put the measurement next to each number if including a range.

If you need to, use a decimal in dosage measurements.

Dosage examples
✅ Good examples ❌ Bad examples
✅ Good examples The usual dose is one or two 200mg tablets 3 times a day. ❌ Bad examples The usual dose is 1 or 2 200mg tablets 3 times a day.
✅ Good examples The usual dose is 250mg to 500mg. ❌ Bad examples The usual dose is 250 to 500mg.
✅ Good examples The usual starting dose is 2.5mg once a day. ❌ Bad examples The usual starting dose is 2 1/2mg once a day.

Concentration measurement

Use 'millimoles per litre (mmol/l)' or 'mmol/l (millimoles per litre)' when first mentioned on a page. Then use 'mmol/l' after.

Ranges

For ranges, use the format of 2mm to 4mm, for example. Do not use 2 to 4mm or 2-4mm.

Temperature

We use Celsius for temperature. For example, 'A temperature of 38 degrees Celsius or higher.'

Measurement symbols

For symbols check:

Dates and times

For time, we use am and pm, with no space.

For dates, we use this format: 18 February 2026.

Spell out months in full. Assistive technologies can read out shortened months (Jan, Feb and so on) in inconsistent and sometimes confusing ways.

If times are included, use a comma to split the sentence.

For example:

  • Wednesday 1 June, 10.30am to 11.30am
  • Wednesday 1 June, 7pm to 8pm

If only the day and date are included, no comma is needed.

For example:

  • Wednesday 1 June 2024

Times

Time format examples
✅ Good examples ❌ Bad examples
✅ Good examples 5.30pm ❌ Bad examples 1730hrs, 5:30p.m.
✅ Good examples Midnight ❌ Bad examples 00:00, 12am
✅ Good examples Midday ❌ Bad examples 12noon, 12pm
✅ Good examples 6 hours 30 minutes ❌ Bad examples 6.5hrs

Today

If you write 'today' in a news article, add the date in brackets. For example, 'The HSE announced today (1 March 2026) that …'