Numbers

Version 7.1 by Lizzie Bruce on 2019/05/22 10:39

Following this helps:

  • people in a hurry – clear, specific data and numbers are quicker to scan and comprehend.
  • people who are stressed – not having to decipher fractions makes content easier to absorb. 
  • people who are multi-tasking – if your attention's divided clear, specific data is more helpful.
  • cognitive impairments – easy to understand figures carry less cognitive load
  • visual impairments – numerals are easy to spot in a smaller visual focus field


Guidance

1. Use numerals instead of words for numbers.

2. Choose clear typography.

3. Be specific with data.

4. Use percentages.

5. Use "to" for number ranges, not a hyphen.

6. Use years and months not just months.

7. Use a space before KB and MB.

Usability evidence


1. Use numerals instead of words for numbers.

They are easier to scan read. It's more consistent to always use numerals rather than have a variety of rules for different sentence structures.

Example:

"You’ll be shown 14 clips that feature everyday road scenes.

There will be:

1 developing hazard in 13 clips
2 developing hazards in the other clip"

2. Choose clear typography.

"1" and "I" can look the same depending on the typeface, as can "0 and "O", so choose a typeface where these characters look sufficiently different and unique. Test with users if you're not sure.

Avoid using 0 and 1 if they could cause confusion with letters. Make sure passcodes do not include characters that can cause letter confusion.

3. Be specific with data.

Be specific and consider the context. 20% of 10 people is very different to 20% of 100.

Example:

"20 people" not "20% of the survey group"

Keep data as accurate as possible, 2 decimal places is recommended.

Example:

4.03 MB

4. Use percentages.

Use a % sign for percentages: 50%

5. Use "to" for number ranges, not a hyphen.

Use ‘500 to 900’ and not ‘500-900’.

Addresses: use ‘to’ in address ranges: 49 to 53 Cherry Street.

6. Use years and months not just months.

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

Example:

"1 year 6 months" not "18 months", "a year and a half" or "1.5 years".

Below 1 year, use months: 

"6 months old"


7. Use a space before KB and MB

Use KB with a space before for anything under 1 MB. Use MB with a space before for anything over 1 MB.

Examples:

569 KB not 0.55 MB
4 MB not 4096 KB


Usability evidence

'The innate mind: Structure and Contents Part III > Number and natural language', 2005

'Formatting the value of a quantity', 2006

'Show numbers as numerals when writing for online readers', J. Nielson, 2007

'Knowledge of number and knowledge of language: Number as a test case for the role of language in cognition', De Cruz, H. and Pica, P., 2008. Locked

'Low levels of numeracy are a long-term problem for the UK', National Numeracy update, National Numeracy YouGov Survey 2014, data sources: Skills for Life 2011PIAAC 2014,

GOV.UK Content principles, UK Government, 2016

GOV.UK Style guide A to Z, UK Government, 2016

'Numeracy and decision making’, Peters, E., D. Västfjäll, et al., Psychological Science, 17(5), pp. 407 to 413. 2006. Locked.

'Less is more in presenting quality information to consumers', Peters, E., N. Dieckmann, et al, Medical Care Research and Review, 64 (2), pp.169 to 190. 2007

'‘‘A 30% chance of rain tomorrow’’: How does the public understand probabilistic weather forecasts?', Gigerenzer, G., Hertwig, R., van den Broek, E., Fasolo, B., & Katsikopoulos, K.V., Risk Analysis, 25, 623 to 629, 2006

‘The Effect of Type Size and Case Alternation on Word Identification’, Smith, Lott and Cronnell, 1969. Semi-locked: free to access online with MyJSTOR account.

‘Case alternation impairs word identification’ Coltheart, M. and Freeman, R. 2013

'Can you tell your 1 from your l? Why letter legibility is key in type design', Design Week analysis of Thomas Bohm’s report on typographical usability.