What is Cost Per Thousand (Audio CPT)?
Cost Per Thousand (CPT), also known as Cost Per Mille (CPM), is a pricing model used in radio and audio advertising where advertisers pay for every 1,000 listener impressions or exposures their ad receives. In the UK media buying landscape, CPT is a fundamental metric for evaluating the cost-effectiveness of audio campaigns across commercial radio stations, streaming services, and podcast platforms.
Why CPT Matters in Audio Advertising
CPT enables media buyers to compare the efficiency of different audio channels and stations on a standardised basis. Rather than negotiating fixed spot rates, CPT provides a transparent, volume-based approach that scales with audience size. This is particularly valuable in the UK market, where radio audiences vary significantly between national stations (like Capital FM, BBC Radio 1) and regional outlets.
Using CPT helps agencies justify spend allocation and demonstrate ROI to clients. A lower CPT indicates better value, though quality of audience and contextual fit must also be considered alongside the metric.
How CPT is Calculated
The formula is straightforward:
CPT = (Total Cost ÷ Total Impressions) × 1,000
For example, if a podcast campaign costs £5,000 and generates 2 million listener impressions, the CPT would be £2.50.
CPT vs Other Audio Metrics
While CPT focuses on impression volume, other metrics serve different purposes. Cost Per Engagement (CPE) measures interaction, whilst Cost Per Acquisition (CPA) tracks conversions. CPT is most useful for brand awareness campaigns where reach and frequency are primary objectives.
UK Radio and Audio Context
In the UK, CPT rates vary widely depending on the medium:
- Commercial Radio: Rates typically range from £2–£15 CPT depending on station size and daypart
- Streaming Platforms: Often cheaper, ranging from £1–£5 CPT due to larger audiences
- Podcasts: Premium shows may command higher CPT (£5–£20+) due to engaged, niche audiences
- BBC Radio: Not traditionally sold on CPT basis; sponsorship and insertions follow different models
Best Practices for Audio CPT Buying
When negotiating CPT rates, consider audience demographics, time of day, and campaign duration. Longer campaigns and off-peak slots typically command lower CPT rates. Always cross-reference CPT against audience quality metrics like listenership data from RAJAR (Radio Joint Audience Research) to ensure you're reaching your target demographic efficiently.
CPT should form part of a broader media strategy rather than the sole decision-making factor. Combining CPT data with qualitative insights about station positioning and listener intent produces more effective campaigns.