You budgeted for five SDRs. Plan for the three you'll have.

If you've written a sales hiring plan for next year, it probably shows five SDRs starting in January and working at full pace from about April. The pipeline target then gets built on five people's worth of meetings for the rest of the year. We often hear what happens next: by the autumn one or two of those seats are empty or being refilled, and the target hasn't moved.

On median industry numbers, two of five SDRs leave within a year. A plan that works counts productive seat-months, assumes some of them will go missing, and decides in advance how each gap gets covered.

What does 40% SDR attrition mean for a five-person team?

It means two of your five should be planned as leavers. The Bridge Group's 2025 SDR study surveyed 351 B2B companies and found median annual attrition of 40% in 2024. The middle half of companies sat between 21% and 57%, so even a well-run team should expect at least one departure in a year.

The breakdown is more useful than the headline. Of the 40 points, 13 were involuntary (people let go), 11 were voluntary (people who chose to leave) and 16 were promotions, usually into an AE role. So the biggest single reason a seat empties is that the person did well. Average tenure was 1.9 years, the highest the study has recorded since the early 2010s.

Two caveats before you lift the number into a spreadsheet. The sample is 78% North American and 83% SaaS, with median revenue of $47M, so a 30-person UK firm may look different. And the same study found only 60% of SDRs hit quota, the lowest figure in its history. Attrition and attainment are separate discounts, and most plans apply neither.

Count seat-months, not heads

A headcount plan says "five SDRs". A capacity plan says how many months of full-pace selling you'll get from them, and that second number is the one your pipeline target depends on. Every month a seat is empty, recruiting or ramping comes off it.

The timing of each departure matters as much as the count. Someone who leaves in March, before they've reached full pace, costs you almost nothing in output this year and a lot in money. Someone who leaves in September takes five productive months of relationships with them, and the replacement won't be at full pace until the following spring.

The same sum at different attrition rates shows how wide the range is:

At the 75th percentile you're running at 60% of the plan before anyone misses quota.

What leaves with the SDR

When an SDR leaves, the open conversations they were having usually stop. Their prospects were replying to a person, and that person's inbox is now closed. Unless someone picks up the thread that week, the half-booked meetings and the "come back to me in Q3" replies go cold. A replacement starting three months later doesn't know those conversations existed, so they start again from a cold list.

In the UK the gap has cost more since 6 April 2025, when employer National Insurance rose from 13.8% to 15% and the threshold fell from £9,100 to £5,000. You pay that on the outgoing SDR's notice, on the replacement's full salary through ramp and on any overlap.

A planning checklist for the team you'll actually have

Most of this is work you can do in the planning cycle, before anyone has resigned. Run your own plan against these:

1. Write the target in full-pace seat-months. Take your headcount, subtract three months of ramp per hire, then take off the attrition you expect. Use 40% unless you have two years of your own data.
2. Set the backfill trigger now. Decide that the day someone resigns, the role is re-advertised that week with the spec already written. Every week spent getting sign-off adds a week to the gap.
3. Write the playbook down. A replacement who inherits a tested target list, the messages that got replies and a log of objections ramps faster than one who inherits a login.
4. Make handover a CRM job. Every live conversation should have a next step and a date in the CRM, so a manager can reassign them in a morning when someone leaves.
5. Check your manager's capacity. The Bridge Group found an average of 6.4 SDRs per first-line leader, falling to 3.6 at companies under $5M revenue. If your sales leader is also carrying a number, five SDRs plus two rounds of recruiting is a lot to ask.
6. Decide who books meetings while a seat is empty. The founder, an AE or an outside team. Leaving it undecided usually means nobody does it.

When hiring in house is still the right call

Plenty of teams should build, and this maths doesn't change that. In-house tends to be the better long-term choice when you have a sales leader with time to manage and coach, and a playbook a new starter can follow from their first week. With both in place, ramp shortens, people stay longer, and a resignation is a gap of weeks rather than a reset.

It's also right when SDR is meant as a training ground. If you hire SDRs so that the good ones become your next AEs, promotion-driven attrition is the system working. In that case, plan the backfill on the same date you plan the promotion, and budget for one more hire a year than the org chart shows.

The comparison of outsourced and in-house SDR costs sets out the cases on each side.

Where an outside team fits in the plan

An outside team is one way to fill the seat-months your plan will lose, or to cover them while you build the manager and the playbook. That's a service we sell, so read this paragraph as the commercial part. ORRJO's lead generation team starts outreach within 2 weeks of kickoff, and first qualified meetings typically land within 2 weeks of launch. Our fastest first qualified meeting on record came three days from kick-off, for Jua.

Some companies run both. The outside team books meetings from the first quarter and keeps booking while seats are refilled, and the in-house SDRs ramp on messages that have already been tested. If your plan has a January start date in it, the calendar has its own problem, which we work through in hire an SDR in January and they hit full pace in July.