ASR (Answer-Seizure Ratio) is a key performance metric in voice termination that measures the percentage of attempted calls that are successfully answered. Calculated as (answered calls / total call attempts) ร 100, ASR is a primary indicator of route quality and carrier network health. High-quality Platinum routes from carriers like IDT Express typically achieve ASR above 60โ70% for most destinations. Low ASR indicates routing problems, congestion, or regulatory blocking on a given route.
ASR (Answer-Seizure Ratio) measures the percentage of outbound call attempts that are successfully answered by the called party. It is calculated as: (number of answered calls รท number of call attempts) ร 100. For example, if 1,000 calls are attempted and 650 are answered, the ASR is 65%. ASR is one of the primary metrics used by wholesale voice carriers and their customers to assess the health and quality of a voice route. A persistently low ASR signals problems with call delivery, network congestion, or regulatory blocking on a given carrier or destination.
A good ASR varies by destination and use case. For major developed market destinations (US, UK, Western Europe) on premium routes, an ASR above 60โ70% is generally considered healthy for outbound business calls. Developing market destinations typically show lower ASR (40โ55%) due to network conditions and higher proportions of unanswered calls. Contact centres with high outbound dial volumes typically target ASR above 60% for their primary destinations. An ASR below 40% on a route that previously performed well usually indicates a network problem or carrier quality degradation requiring investigation.
Low ASR can result from several factors: network congestion at the terminating carrier causing busy signals or failed connections; regulatory blocking of the originating number or prefix (common when numbers are flagged for spam); poor route selection with too many intermediary carrier hops increasing the chance of failure; destination-side issues such as the called number being out of service or the subscriber being unreachable; or CLI problems causing calls to be rejected or screened by the recipient. Diagnosing low ASR typically requires route analysis and SIP error code review to identify the specific failure reason.
ASR measures call completion, not call audio quality โ a call with poor audio but successfully answered still counts positively for ASR. However, the two are related: routes with high ASR typically use direct carrier interconnections and well-maintained infrastructure, which also correlates with lower latency, better CLI pass-through, and fewer in-call quality issues such as echo or packet loss. Routes optimised purely for low cost (used in LCR configurations without quality gates) often show both lower ASR and lower audio quality, as they rely on longer carrier chains with more potential failure or degradation points.
