Most small manufacturers carry two costs for every made item without realising. The standard cost sits in the item master, typed in when the product was created. The actual cost emerges from the last works order, tracking material usage, hours clocked, and overhead absorbed. These figures should align. Left unchecked, they diverge, creating a gap that erodes margins.
What each cost is for
Standard cost is a calculated expectation. It assumes the bill of materials (BOM) is accurate, the route is followed, and components are priced at agreed rates. It enables quoting before production and provides a benchmark for variance analysis. As IAS 2 states, “Standard costs take into account normal levels of materials and supplies, labour, efficiency and capacity utilisation. They are regularly reviewed and, if necessary, revised in the light of current conditions.”
Actual cost records what a specific job consumed: components at their stock value, hours at work centre rates, and applied overhead. This figure reveals whether a job made money. While actual cost informs financial reporting, it cannot guide future quotes due to its variability.
Average or FIFO cost, used for stock valuation and cost of goods sold, blends historical receipts. It is not a quoting tool. Under IFRS and UK GAAP (as per IAS 2 and FRS 102), standard costing is permitted if it approximates actual cost and is reviewed regularly. A static standard, unchanged since product creation, violates this principle.
Why a typed-in standard drifts
A standard cost is a snapshot of a dynamic system. Consider these common scenarios:
- Component price changes: A supplier increases the price of a steel bracket from £8 to £10. The next purchase order reflects this, but the parent product’s standard cost still uses £8. The BOM line scrap rate might also change—for example, from 5% to 8% due to process inefficiencies—increasing material costs further.
- Route modifications: Adding a polishing step to a casting route adds 0.5 hours per unit at a work centre rated at £25/hour. The works order estimate includes this, but the standard cost remains unchanged.
- Overhead adjustments: Year-end overhead absorption rates rise from £15 to £18 per direct labour hour. New job estimates use the updated rate, but the standard cost still applies the old figure.
Over time, these small discrepancies compound. For example, a product with a £200 standard cost in 2023 could see its actual cost rise to £225 by 2024 due to cumulative changes in material prices, scrap rates, and overhead. Quotes based on the outdated standard now understate true costs, creating false variances in post-production analysis.
What a cost roll-up is
A cost roll-up rebuilds the standard cost from current BOMs, routes, and rates. Here’s how it works:
- Component costs: For each component, the roll-up uses the current standard cost (or purchase price) multiplied by the BOM quantity, adjusted for scrap. For example, a part with a 10% scrap rate requires 1.1 units per finished product, not 1.0.
- Work centre rates: Setup times and run times from the route are costed using current hourly rates. As Microsoft Learn explains, “setup time rates apply for each lot. Therefore, you must prorate the routing setup time for each operation over the lot size.” A 2-hour setup for a 200-unit batch adds 0.01 hours per unit.
- Overhead application: Overhead is absorbed using the same rules as job costing. If a product’s route includes 3 direct labour hours, and the overhead rate is £20/hour, £60 is added to the standard cost.
Tools like Business Central’s “Calculate Standard Cost” and Odoo’s “Compute Price from BoM” automate this process. As Odoo’s documentation states, “Odoo computes MO costs based on the configuration of the BoM used to manufacture a product. This includes the cost and quantity of components and operations listed on the BoM, in addition to the operating costs of the work centers where those operations are carried out.”
The roll-up process is bottom-up: changes to a sub-assembly’s cost automatically update parent items. For example, a gearbox’s cost increase due to a bearing price hike would ripple up to the machine it assembles into. Microsoft Learn describes its all-levels calculation this way: “Recalculate costs for the entire BOM structure. Starts from the lowest-level purchased or produced items and rolls costs up through every intermediate subassembly to the top-level item.”
When to re-run it
Standard cost roll-ups should follow material changes:
- Supplier repricing: After a vendor increases the price of a common component like motors or fasteners.
- Engineering changes: Once a revised BOM or route is approved.
- Annual overhead updates: At year-end when new absorption rates are set.
- Quarterly reviews: For top-selling products, to catch smaller drifts.
For example, a furniture maker might schedule roll-ups every January after supplier contracts renew and again in July if major route changes occur. Microsoft Learn notes that “Controllers can preview cost changes before and after the roll-up to identify unacceptable deviations,” which is the review step that makes the whole exercise safe.
Where to start
Test the process on a single product with a multi-level BOM. Take a simple example: a steel shelf with four components (posts, shelves, brackets, screws) and two operations (cutting and assembly). Manually calculate the standard cost using current component prices, scrap rates, and work centre rates. Compare this to the system’s standard cost. A £5 difference in a £100 product signals a 5% quoting error.
If discrepancies exist, investigate their root causes. A missing component cost in the BOM might make sub-assemblies appear cheaper than they are. Outdated scrap rates could understate material usage. Correcting these ensures quotes reflect reality.
How Brytebuild handles cost roll-ups
Brytebuild rolls the standard cost from the bill of materials and the route on each item’s Cost & valuation tab, using current component costs, scrap-adjusted quantities and work centre rates, and shows the proposed figure against the current standard before anything changes. When you apply it, the standard is written bottom-up with a cost snapshot, which is the record of regular review that IAS 2 and FRS 102 expect. See the costing and margin guide for how Brytebuild integrates standard, actual, and average costs.