How do you calculate regional demand forecast?

Multiply panels demanded per cycle by the number of selling cycles to get gross demand, then multiply by in-stock service level and order fill rate. Here 4 x 480 = 1,920 gross, x 90% x 97% = about 1,676 fillable panels.

What is the difference between gross and fillable demand?

Gross demand, 1,920 panels here, is total signaled demand. Fillable demand, about 1,676, is what you actually ship after roughly 192 panels lost to stockouts and 52 lost to returns and short-fills.

What service level should I plan a region to?

Building-product distributors commonly target 90-95% in-stock service on core SKUs. The 90% default is a reasonable regional target; pushing higher requires more safety stock, which the forecast can help justify.

How do stockouts and returns affect my regional number?

In this forecast stockouts cut about 192 panels and returns and short-fills cut roughly 52, so fillable demand is about 244 panels below the 1,920 gross signal. Plan production and inventory against 1,676, not 1,920.

Should I plan production to gross or fillable demand?

Plan capacity and inventory to fillable demand plus a safety buffer. Building to gross demand overstocks regions and ties up cash in slow-moving color and profile combinations.

Why separate service level from fill rate?

Service level captures whether product was on the shelf when ordered; fill rate captures returns and short-ships on orders you did serve. They are different leakage points and each needs its own fix.

Roofing, Siding & Exterior Building Products calculator

Regional demand forecast Calculator

Regional Demand Forecast projects how many roofing or siding panels a territory will actually take once stockouts and returns are accounted for. Demand planners and regional sales-ops leads at exterior building-product makers use it to translate raw demand signals into a shippable, sellable number by market. Weather-driven, seasonal siding and roofing demand is famously lumpy, so a gross forecast that ignores in-stock service level overstates what a region can absorb. This calculator discounts gross demand for service and fill so distribution and production plan against real, fulfillable volume.

What this calculator does

Estimate regional demand forecast for roofing, siding and exterior building products using production-ready inputs so teams can confirm whether capacity can cover demand before committing the schedule.
Use it when regional demand forecast in roofing, siding and exterior building products is being asked to take on more work and you need to know if there is room.
It computes fillable regional demand by discounting gross forecast panel volume for in-stock service level and order fill (non-return) rate.

Formula used

Gross regional demand forecast capacity = regional demand forecast output per cycle × available regional demand forecast cycles
Good regional demand forecast capacity = gross capacity × expected regional demand forecast uptime × expected regional demand forecast first-pass yield

Inputs explained

Panels demanded per selling cycle:
Selling cycles in the forecast horizon:
In-stock service level:
Order fill (non-return) rate:

How to use the result

Use it when allocating production to regions, sizing regional inventory, or setting a realistic sales forecast that reflects service and returns.
It applies flat service and fill rates across the horizon and will not capture a seasonal storm spike or a single large contractor order unless those are built into the per-cycle demand.

Current U.S. benchmarks

U.S. housing starts run at 1,177k per year (Census, May 2026), down 8.7% from a year earlier, the demand driver for building products.

Common questions

How do you calculate regional demand forecast? Multiply panels demanded per cycle by the number of selling cycles to get gross demand, then multiply by in-stock service level and order fill rate. Here 4 x 480 = 1,920 gross, x 90% x 97% = about 1,676 fillable panels.
What is the difference between gross and fillable demand? Gross demand, 1,920 panels here, is total signaled demand. Fillable demand, about 1,676, is what you actually ship after roughly 192 panels lost to stockouts and 52 lost to returns and short-fills.
What service level should I plan a region to? Building-product distributors commonly target 90-95% in-stock service on core SKUs. The 90% default is a reasonable regional target; pushing higher requires more safety stock, which the forecast can help justify.
How do stockouts and returns affect my regional number? In this forecast stockouts cut about 192 panels and returns and short-fills cut roughly 52, so fillable demand is about 244 panels below the 1,920 gross signal. Plan production and inventory against 1,676, not 1,920.
Should I plan production to gross or fillable demand? Plan capacity and inventory to fillable demand plus a safety buffer. Building to gross demand overstocks regions and ties up cash in slow-moving color and profile combinations.

Last reviewed 2026-05-12.