Kaizen Costing and Continuous Cost Improvement
The Japanese manufacturing discipline that drives cost down during production through many small, continuous improvements - the operating-phase partner to target costing, which designs cost out before a product is ever built.
Kaizen costing is the practice of setting and pursuing a planned rate of cost reduction across the production life of a product, achieved through continuous, incremental improvements on the shop floor rather than a single redesign. The word kaizen means "change for the better", and the method was formalised in Japanese manufacturing - closely associated with Toyota and documented by Yasuhiro Monden. Where target costing engineers cost out of a product before launch, kaizen costing keeps pushing it down afterward: each period carries a kaizen cost-reduction target, usually a small percentage of current cost, that operators and teams are expected to meet through better methods, less waste, shorter setups and steadier flow. The two methods form a chain - target costing sets the entry cost, kaizen costing bends the cost curve downward through the whole production run - and both answer to the same market-driven ceiling on what a product is allowed to cost.
Improving the cost of what already exists
Standard costing asks whether actual cost met a fixed engineering standard, and treats holding the line as success. Kaizen costing rejects the standing standard: it assumes that today's cost is never the floor, and that a modest reduction is expected every period, indefinitely. The reference point is not a static standard but the previous period's actual cost, ratcheted down by a target. Meeting last period's cost is not good enough; the goal is to beat it, and then beat that.
The improvements are deliberately small and local. Kaizen costing does not wait for a capital project or a product relaunch. It harvests cost from the everyday - a shorter changeover, a fixture that removes a step, a layout that cuts walking distance, a defect chased back to its cause. Responsibility sits with the people doing the work, supported by industrial engineering, because they see the waste first. Individually each gain is trivial; compounded across a workforce and a year, they move the number that matters.
Target costing designs cost out; kaizen costing drives it down
Target costing works in the design phase, before a single unit is made. It starts from the price the market will bear, subtracts the required margin, and derives an allowable cost that the product must be engineered to hit. The great majority of a product's lifetime cost is locked in here, in the choices of design, materials and process. Once production begins, most of that cost is committed and hard to move.
Kaizen costing takes over from launch. It accepts the design as given and attacks the cost that remains variable in the making - labour, materials yield, energy, rework, setup. Its lever is continuous improvement rather than redesign, and its horizon is the full production life of the product. In Monden's account the two are complementary stages of a single cost-management system: target costing sets an aggressive entry point, kaizen costing prevents cost from drifting back up and instead pulls it steadily lower. Neither works alone. A brilliant target cost erodes without kaizen discipline; kaizen effort on a poorly designed product hits a wall the redesign should have removed.
A kaizen reduction target across a year
Take a component that currently costs €40.00 a unit to produce, made at 100,000 units a year, so annual production cost is €4,000,000 (illustrative figures, not client data). Management sets a kaizen cost-reduction target of 3% for the year, allocated evenly across four quarters at roughly 0.75% each.
The full-year goal is a €120,000 reduction (3% of €4,000,000), taking unit cost from €40.00 toward €38.80 by year end. Quarter by quarter the target ratchets from the prior actual: about €30,000 of savings each quarter, found in specific improvements - a €0.30 material-yield gain from less scrap, a €0.40 labour gain from a shorter setup, a €0.50 gain from fewer defects and reduced rework. If the first quarter delivers only €24,000, the shortfall of €6,000 is not written off; it rolls into the pressure on the next period, because the reference cost for Q2 is the Q1 actual, not the original standard. Over the run, a sustained 3% annual pace compounds: a €40 unit cost held to that rate reaches roughly €36.5 within three years, entirely from incremental shop-floor gains rather than any redesign.
Kaizen costing versus target costing versus standard costing
| Dimension | Target costing | Kaizen costing | Standard costing |
|---|---|---|---|
| When it acts | Design phase, before production | Production phase, across the product life | Production phase, per period |
| Cost reference | Market-derived allowable cost | Previous period's actual, ratcheted down | Engineered standard, held fixed |
| Main lever | Design, materials, process choice | Continuous incremental improvement | Variance control against the standard |
| Attitude to current cost | Not yet committed - design it out | Never the floor - beat it every period | Acceptable if the standard is met |
| Who owns it | Design and cross-functional teams | Operators and shop-floor teams | Management accounting and supervisors |
The table shows why the three are not rivals but a sequence. Target costing decides what a product is allowed to cost; kaizen costing keeps that promise through the run; standard costing, in its classic form, only asks whether a frozen expectation was met. Together the first two form a continuous market-to-shop-floor cost chain, which is the wider theme of this encyclopedia: understanding true cost-to-serve, reading a customer whale curve, and grounding both in time-driven activity-based costing (TDABC) so that product and customer profitability rest on real resource use rather than an unchallenged standard.
When kaizen costing earns its keep
Strengths. Kaizen costing sustains cost pressure long after launch, when standard costing tends to declare victory. It engages the people closest to the waste, so improvement ideas come from where the work happens, and it builds a culture in which cost reduction is continuous and expected rather than a crisis response. In a stable, repetitive manufacturing setting with a long production run, the compounding effect of small gains is substantial and durable.
Limits. The method assumes there is cost still to be squeezed from the process; on a well-designed, mature product the easy gains eventually run out and the pressure can feel relentless to the workforce if not managed with care. It is weakest where the real cost driver is design or complexity that kaizen cannot reach - that cost belonged to the target-costing stage. And a target expressed only as a blanket percentage can push teams toward corner-cutting rather than genuine improvement unless quality and safety are protected as hard constraints.
Common questions about kaizen costing
- What is kaizen costing?
- Kaizen costing is a cost-management method that sets a continuous cost-reduction target for a product during its production phase and pursues it through many small, incremental improvements on the shop floor. The reference is the previous period's actual cost, ratcheted down each period, rather than a fixed engineering standard.
- How is kaizen costing different from target costing?
- Target costing works in the design phase and engineers cost out of a product before it is made, starting from the price the market allows. Kaizen costing works during production and drives the remaining cost down through continuous improvement. Target costing sets the entry cost; kaizen costing keeps bending the cost curve lower across the production run.
- How is kaizen costing different from standard costing?
- Standard costing compares actual cost to a fixed standard and treats meeting that standard as success. Kaizen costing refuses to treat any cost as the floor: it expects a reduction every period and uses the prior actual cost, lowered by a target, as the new reference. One defends a static expectation; the other assumes cost should always fall.
- Who is associated with kaizen costing?
- The approach grew out of Japanese manufacturing practice, most closely associated with Toyota, and was documented and formalised in the management-accounting literature by Yasuhiro Monden, alongside broader work on target costing and lean production systems.
- Where does kaizen costing work best, and where does it struggle?
- It works best in stable, repetitive manufacturing with long production runs, where small gains compound over time and shop-floor teams can see and remove waste. It struggles when the dominant cost driver is locked in by design or complexity, which belongs to the target-costing stage, and when a blanket percentage target risks quality unless safeguards are set.
References
Monden, Y. Toyota Production System and Cost Reduction Systems: Target Costing and Kaizen Costing (foundational treatment of kaizen costing). · Imai, M. Kaizen: The Key to Japan's Competitive Success (the kaizen philosophy of continuous improvement). · Horngren, C. T., Datar, S. M. & Rajan, M. V. Cost Accounting: A Managerial Emphasis (kaizen and target costing in cost management). · Cooper, R. & Slagmulder, R. Target Costing and Value Engineering (design-phase cost management and its link to continuous improvement). · CIMA, Official Terminology (definitions of kaizen costing and target costing).