Channel guideSales · Collections · Renewals · Surveys · Proactive service

Outbound contact centre staffing

Q: How do you calculate the number of agents for an outbound contact centre?

Outbound agent sizing is target-driven, not queue-driven. The formula: agents = (daily contact target / right-party contact rate / contacts per agent per hour). Or in steps: (1) Daily contacts target ÷ right-party contact rate (RPC%) = total dials needed. (2) Total dials ÷ average dials per agent per hour ÷ productive hours = agents needed. Example: 1,000 contacts target, 35% RPC rate → 2,857 dials needed. At 25 dials/agent/hour, 8h shift, 80% productive: 2,857 ÷ (25 × 8 × 0.80) = 17.9 → 18 agents.

Q: What is the Ofcom rule on abandoned calls for outbound contact centres?

Ofcom's persistent misuse rules require UK outbound contact centres to keep the abandoned call rate below 3% of all live calls in any 24-hour period. An abandoned call occurs when a predictive dialler connects a customer but no agent is available to take the call within 2 seconds of the customer speaking. If the call is abandoned, the dialler must play a specific message and cannot call the same number more than once per day. Breaching the 3% threshold persistently constitutes an offence under the Communications Act 2003. This is why predictive dialler pacing algorithms must balance agent utilisation against abandonment compliance.

Q: What is the difference between a predictive dialler and a power dialler?

A power dialler calls one number per available agent — as soon as an agent becomes free, the dialler places one call. This eliminates the risk of an abandoned call (the agent is always available when the call connects) but reduces efficiency because agents wait for calls to connect. A predictive dialler dials multiple numbers simultaneously based on a mathematical prediction of agent availability, aiming to have a call connecting just as an agent becomes free. Predictive diallers achieve higher agent utilisation (85–92% talk time vs. 60–75% for power diallers) but carry a risk of abandoned calls when predictions are wrong.

Q: What is a good right-party contact (RPC) rate for an outbound centre?

Right-party contact (RPC) rate benchmarks depend heavily on data quality, campaign type, and time of day. For debt and collections campaigns with good data quality: 25–40% RPC on prime-time dials (10–12h, 15–19h). For sales and renewals campaigns: 15–30% RPC. For research or survey campaigns with fresh opt-in data: 20–40% RPC. The most important variable is data recency — stale data (over 6 months old) can reduce RPC to 8–12% regardless of other factors. RPC below 10% typically signals a data quality problem, not a dialling strategy problem.

Outbound staffing is not Erlang C. Inbound queues form when demand exceeds capacity; outbound staffing is about hitting a daily contact target from a campaign list. The key variables are the right-party contact rate, dialler type, and agent talk-time efficiency — not queue mathematics.

Why Erlang C does not apply to outbound

Inbound (Erlang C)

→Customers arrive unpredictably
→Agents wait for calls to arrive
→Service level is the primary constraint
→Erlang C models the queue

Outbound (target model)

→Agents call from a list
→Customers receive calls — no queue
→Daily contacts target is the primary constraint
→Agent count = target ÷ contacts per agent per day

Outbound agent sizing formula

Step-by-step calculation

Daily contact target1,000 right-party contacts

÷ Right-party contact rate35% RPC → 2,857 total dials

÷ Dials per agent per hour25 dials/h (predictive dialler)

÷ Productive hours per shift8h × 80% productive = 6.4h

= Agents required2,857 ÷ (25 × 6.4) = 17.9 → 18 agents

RPC rate is the most variable input. A 10pp change in RPC (35% → 25%) increases dials needed by 40% — which either requires more agents or a longer dialling window. Data quality is the fastest lever on RPC.

Dialler types and staffing implications

Predictive dialler

85–92% talk time

Uses statistical prediction to dial multiple numbers simultaneously. The algorithm must balance utilisation against Ofcom's 3% abandoned call limit. Staffing calculation accounts for expected idle time between connects.

Risk: Abandoned calls if prediction wrongBest for: High-volume, time-sensitive campaigns (debt, renewals) with large call lists

Power dialler

60–75% talk time

Dials one number per available agent — agent is always ready when the call connects. No abandoned call risk. Lower throughput than predictive. Simple sizing: contacts/day = agents × connects/hour × productive hours × RPC rate.

Risk: No abandoned calls; lower efficiencyBest for: Regulated campaigns, high-value leads where abandoned calls are unacceptable

Preview dialler

45–60% talk time

Agent sees record and clicks to dial — used when agents need to review information before calling. Lowest occupancy of all dialler types. Sizing is straightforward: contacts/day = agents × (contacts per hour reviewed and dialled) × productive hours.

Risk: Lowest efficiency; agent controls timingBest for: Complex sales, legal-sensitive conversations, high-value B2B outbound

Manual / progressive

35–55% talk time

Used for very small lists or highly regulated contexts. Agent dials manually; no automation. ACD data used to track handle time and volume. Sizing: target contacts ÷ (contacts per agent per day) = agents, with contacts per day validated from historical performance.

Risk: Lowest compliance risk; slowest throughputBest for: Very small lists; consultative outreach; situations where dialler cannot be justified

Ofcom compliance for predictive diallers

UK persistent misuse rules (Ofcom)

Max 3% abandoned call rate

No more than 3% of connected calls may be abandoned (no agent available within 2 seconds) in any 24-hour period. Calculated as abandoned ÷ total live calls connected.

2-second rule

If no agent is available within 2 seconds of the called party answering, the call is classified as abandoned. The dialler must play an informational message.

No repeated calling

An abandoned call number must not be called again that day. The dialler system must flag and suppress the number within the campaign.

Informational message requirement

Abandoned calls must receive a message identifying the company calling and providing a freephone number. Silence or a hangup is not compliant.

Ofcom can issue fines of up to £2 million for persistent misuse breaches. The compliance constraint on predictive diallers means the pacing algorithm must be conservative enough to stay under 3% abandoned call rate — which is directly tied to how accurately it can predict agent availability. More agents = more accurate prediction = lower abandoned call rate at the same utilisation.

Key outbound metrics and benchmarks

MetricTypical rangeWhat drives it

Right-party contact (RPC) rate15–40%

Data quality and recency. Stale data drops RPC to 8–12%.

Contacts per agent per hour8–20

Dialler type, RPC rate, and AHT are the main drivers.

Talk time (predictive)85–92%

The predictive algorithm's quality and list penetration.

Talk time (power dialler)60–75%

Connect rate and time between calls waiting for connection.

Abandoned call rate< 3% (Ofcom limit)

Dialler pacing aggressiveness vs. agent availability.

Average handle time3–8 min

Campaign type: collections longer than renewals; surveys shorter.

Conversion rateCampaign-specific

Not a WFM metric — owned by sales/commercial, not planning.

Outbound staffing questions

How do you calculate the number of agents for an outbound contact centre?

Agents = daily contact target ÷ RPC rate ÷ dials per agent per hour ÷ productive hours. Example: 1,000 contacts, 35% RPC, 25 dials/h, 6.4 productive hours = 2,857 dials ÷ (25 × 6.4) = 17.9 → 18 agents. The RPC rate is the most variable input — a 10pp drop in RPC increases dials needed by ~30%.

What is the Ofcom rule on abandoned calls for outbound contact centres?

Ofcom's persistent misuse rules require UK outbound operations to keep the abandoned call rate below 3% of all live calls in any 24-hour period. An abandoned call is one where no agent is available within 2 seconds of the customer answering. Breaching this threshold persistently is an offence under the Communications Act 2003 with fines up to £2 million.

What is the difference between a predictive dialler and a power dialler?

A power dialler calls one number per available agent — no abandoned call risk but lower utilisation (60–75% talk time). A predictive dialler calls multiple numbers simultaneously based on predicted agent availability, achieving 85–92% talk time but carrying a risk of abandoned calls if predictions are wrong. Predictive diallers must stay within Ofcom's 3% abandoned call limit.

What is a good right-party contact (RPC) rate for an outbound centre?

Debt and collections with good data: 25–40% RPC on prime-time dials. Sales and renewals: 15–30% RPC. Research/survey with fresh opt-in data: 20–40% RPC. RPC below 10% typically signals a data quality problem — stale data (over 6 months old) is the most common cause.

Also running an inbound operation?

Many blended centres handle both inbound queues and outbound campaigns. Use Erlang C for the inbound queues and the outbound sizing formula above for the campaign teams.

Erlang C calculator →Multi-skill routing guide