Strategic workforce planning has a large literature and a short method. Almost everything that goes wrong with it goes wrong in one of two places: the plan counts growth instead of hiring, or it books people as productive on the day they start. This page is the short method, in the order a budget round actually needs it, for the person who will have to defend the number in a room.
Step one: state today honestly
Headcount now, by role, and the attrition you have actually seen over the last twelve months rather than the figure you would like. Every later number inherits these two, and a plan built on an optimistic attrition rate is short all year in a way that is invisible until the third quarter.
Step two: work out hires, not growth
Net growth plus expected leavers is the requisition count. On a team of a hundred and twenty with meaningful attrition, that difference is routinely larger than the growth itself, and it is the single most common reason a plan that was approved in full still leaves the team understaffed.
Step three: work backwards from time to hire
A requisition approved too late cannot produce a start inside the year. The useful thing to write in the plan is the approval deadline rather than the headcount, because that is the date somebody can miss.
Steps four and five: ramp, then cost
Count the weeks between a start date and full productivity and multiply across the plan, because that is capacity you are paying for and not receiving. Then cost the planned team at a fully loaded rate. The free worksheet on this site does all of this from your own inputs.
Questions people ask about strategic workforce planning
How far ahead should a workforce plan look?
Far enough that a requisition approved at the end of it can still start inside it, which for most teams means at least a year and rarely more than three.
What if the business will not commit to a target?
Plan for the attrition alone. Replacing leavers is not optional and is a large part of the year's hiring whether or not anybody has agreed a growth number.
Is this the same as budgeting?
It feeds it. The plan says how many and when; the budget turns that into money, and the worksheet returns the annual cost so both come from one place.