Changeover Time Reduction (SMED) Calculator
Capacity and cost recovered by cutting changeover time (SMED) — hours freed per year, extra units, the smaller economic batch the new setup allows, inventory reduction and payback on the improvement spend.
How it works
Hours freed = (before − after) × changeovers/week × weeks ÷ 60; new economic batch = old batch × √(after ÷ before); inventory saving = (Δbatch ÷ 2) × unit cost × holding rate; payback = spend ÷ annual benefit
Single-Minute Exchange of Die is the discipline of separating changeover work that can be done while the machine is still running (external) from what truly needs it stopped (internal), then converting and streamlining the internal steps; halving or better is routine. The benefit shows up in two ways. If the machine is a bottleneck, every minute saved is extra saleable output, valued at the contribution margin per hour. If it is not, the real prize is flexibility: because the economic batch size scales with the square root of setup cost, a 90-to-30-minute changeover lets batches shrink by 42% at no penalty, cutting cycle inventory, lead time and the risk of making the wrong thing. Most plants take a mix — some smaller batches, some extra capacity — and fund the cheap fixtures, pre-staged tooling and standard work that make it stick.
Worked example
Twelve 90-minute changeovers a week cut to 30 minutes: 12 hours freed weekly, 600 hours a year worth $108,000 at $180 an hour. Batches can drop from 2,000 to about 1,150 units, freeing $6,400 of inventory and saving $1,600 a year in holding cost; a $12,000 spend pays back in about 1.3 months.
Frequently asked questions
Should I value freed time at the machine rate?
Only if the time is actually used — for more output on a constrained machine (use margin per hour) or by avoiding overtime or a second shift. Otherwise the benefit is flexibility and inventory, not cash from the machine rate.
What reductions are typical?
First SMED workshops usually cut changeovers 50–70% with organisational fixes alone; reaching single-digit minutes often needs quick-release tooling and standardised dies.
Related calculators
Operations planning estimate based on the figures entered; validate against measured shop-floor data before changing staffing, equipment or customer commitments.