Ten to twelve calls a day is a consequence, not a target

Ten to twelve calls a day is the most-repeated number in field sales and one of the least-examined. It gets stated as an expectation, tracked as a KPI, and used in ride-along conversations as evidence about a person. Almost nobody prices the driving that has to happen between the calls, which means almost nobody knows whether the number is achievable in the territory they just handed out.

The whole calculation

Here it is, with assumptions stated so you can substitute your own. I am going to use the values a real field plan gave me; they are conservative and they are arguable, which is the point.

• Field window: 08:00 to 16:00. Eight hours, 480 minutes. Earlier than eight and offices are not open; later than four and the staff you need have gone.
• Lunch: 60 minutes, always. Not optional — a rep who skips lunch for six weeks stops being a rep.
• Minutes per call: 22. Sign in, wait at the desk, five to eight minutes with the provider or the practice manager, then out. This is the median, and the variance is enormous.
• Speed between offices: 26 mph. Mid-morning, in a metro, with lights and parking. Not highway speed, because between-office legs are rarely highway.
• Straight-line to road miles: multiply by 1.2 inside a metro. Roads do not go where the crow flies.
• Minimum leg: 0.6 miles. Two buildings in the same ZIP still cost you a drive, a park and a walk.

So the available time is 480 − 60 = 420 minutes. Each call costs 22 minutes, and n calls need n − 1 legs between offices — the drive out from home base is not a between-offices leg. Let d be the straight-line distance between consecutive offices. Road distance is 1.2d, and at 26 mph that is (1.2d ÷ 26) × 60 ≈ 2.77d minutes per leg.

Solving 22n + 2.77d(n − 1) ≤ 420 gives the number of calls that fit: n = (420 + 2.77d) ÷ (22 + 2.77d), rounded down.

Run it at three densities

At d = 1 mile — a dense medical plaza cluster, several practices in the same complex — the arithmetic says 17 fit. In practice you cap it: a hard limit around 13 exists because a rep making seventeen calls is making seventeen bad ones.

At d = 2.5 miles — a normal tight suburban zone — 14 fit, so the cap binds and you plan 12 or 13. This is the density at which "ten to twelve" is true, and it is why the number entered the folklore in the first place.

At d = 6 miles — a zone that covers two towns — 11 fit, and you are now spending 166 minutes a day driving. At d = 9 miles, 9 fit, and driving is 199 minutes: three hours and nineteen minutes of the working day, behind the wheel.

Between a 2.5-mile zone and a 9-mile zone, the same rep working identically hard produces 13 calls or 9. That is a 30% difference in output caused entirely by a line somebody drew on a map.

Which implies some uncomfortable things

First: if two of your reps are producing different call volumes, the first thing to check is not their work ethic. It is the mean distance between consecutive stops in their territories. That number is computable from the same file you gave them, and until you have computed it you are guessing at the cause.

Second: your best rep may be your most compact rep. This is worth sitting with, because it affects who you promote and who you use as the model in a coaching conversation. Telling a rep with a 9-mile zone to "do what she does" is asking them to change something they do not control.

Third: the highest-leverage change available to most field organisations is not a new incentive or a new CRM. It is re-carving a territory so the mean leg falls by three miles. That is a Tuesday afternoon of work and it is worth more than any sales-skills intervention you can buy.

The two variables you actually control

Look at the formula again: n = (420 + 2.77d) ÷ (22 + 2.77d). Only two things in it are movable.

Minutes per call

Going from 22 to 18 minutes buys you one or two extra calls in a mid-density zone. But this is a dangerous lever, because most of the 22 minutes is not time with the provider — it is sign-in and waiting. Cutting the part you can cut means cutting the conversation, which is the only part that produces anything. The honest way to reduce this number is scheduling: an appointment at a practice that will give you one turns 22 minutes of hoping into 12 minutes of certainty. That is worth pursuing for your top tier and not worth the effort below it.

Distance between stops

This is the big one, and it has two components that get confused. The first is territory shape — how spread out the practices in a zone are — which you change by re-carving. The second is tour order, which you change by sequencing the day properly rather than working down a list.

The second is nearly free and almost universally neglected. A human building a day from a spreadsheet picks a town, scans for names in that town, and writes them in roughly the order they remember the roads. The result crosses itself two or three times, because a person reading a list cannot see a tour. Sequencing the same stops properly — a nearest-neighbour pass, then 2-opt to untangle crossings, then a relocation pass for the one outlier stuck in the middle — routinely takes a meaningful bite out of the day's driving without removing a single call. Same stops. Same providers. Different order.

What to do with the number

Stop stating ten to twelve as an expectation and start stating it as a prediction that the territory either supports or does not. Per zone, per weekday, before the quarter starts: this zone supports 12, this one supports 9. Then measure against that.

This costs you nothing and it changes two things immediately. Reps in spread territories stop being managed as underperformers. And you get, for the first time, a defensible answer to the question of whether you need another head in a region — because "our zones support 43 calls a week and the cadence commits us to 61" is an argument, whereas "the team is stretched" is a feeling.

The arithmetic is four lines long. Do it before your next territory review.