# Spring Festival Supply Buffer Calculator > Source: https://netray.co/tools/china-spring-festival-supply-buffer-calculator > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer Work out how much extra stock to order before Spring Festival so a supplier shutdown does not stop your line. ## Category supply-chain ## Erp SAP / Oracle / Epicor / Infor ## Industry Manufacturing ## Region China ## Audience - Planner - Buyer - Supply chain manager ## Tool **Kind:** calculator **Inputs:** #### Average weekly demand **Key:** demand **Type:** number **Default:** 1200 **Min:** 0 **Step:** 50 **Unit:** units #### Weekly demand standard deviation **Key:** sigma **Type:** number **Default:** 250 **Min:** 0 **Step:** 10 **Unit:** units #### Normal supplier lead time incl. transit **Key:** lt **Type:** number **Default:** 8 **Min:** 1 **Step:** 1 **Unit:** weeks #### Effective shutdown and ramp-up **Key:** shutdown **Type:** slider **Default:** 4 **Min:** 0 **Max:** 8 **Step:** 1 **Unit:** weeks **Help:** Include factory closure, staggered worker return and slow restart. Three to five weeks is common. #### Service level **Key:** service **Type:** select **Default:** 0.95 **Options:** ##### 90% **Value:** 0.9 ##### 95% **Value:** 0.95 ##### 97.5% **Value:** 0.975 ##### 99% **Value:** 0.99 #### Unit cost **Key:** unit_cost **Type:** number **Default:** 18 **Min:** 0 **Step:** 0.5 **Unit:** USD #### Annual holding cost **Key:** carry **Type:** number **Default:** 20 **Min:** 0 **Max:** 60 **Step:** 1 **Unit:** % **Outputs:** #### Service factor (z) **Key:** z **Expr:** normsinv(service) **Format:** decimal #### Safety stock, normal lead time **Key:** ss_normal **Expr:** z * sigma * sqrt(lt) **Format:** integer #### Safety stock, holiday lead time **Key:** ss_holiday **Expr:** z * sigma * sqrt(lt + shutdown) **Format:** integer #### Pre-build to cover shutdown **Key:** prebuild **Expr:** demand * shutdown **Format:** integer **Primary:** true **Description:** Extra units to land before the shutdown starts so the line runs through the gap. #### Extra safety stock for the longer lead time **Key:** extra_ss **Expr:** ss_holiday - ss_normal **Format:** integer #### Total extra inventory to hold **Key:** total_extra **Expr:** prebuild + extra_ss **Format:** integer **Primary:** true #### Value of extra inventory **Key:** extra_value **Expr:** total_extra * unit_cost **Format:** currency #### Holding cost for 8 weeks **Key:** hold_cost **Expr:** extra_value * carry / 100 * 8 / 52 **Format:** currency **Chart:** #### Extra inventory vs shutdown weeks **Type:** line **X:** shutdown **From:** 0 **To:** 8 **Steps:** 9 **Series:** - prebuild - ss_holiday **Disclaimer:** Assumes normally distributed weekly demand and a deterministic shutdown length. Confirm the real closure dates with each supplier and your sub-tier chain. ## Content **Intro:** Every year Chinese factories close for Spring Festival, and the true gap is longer than the public holiday because workers return in waves. If you buy from China, you need extra stock before the closure. This tool sizes it from demand, lead time and the shutdown length. **Sections:** #### How to use it **Body:** Enter weekly demand and its standard deviation, the supplier lead time, and the effective shutdown plus ramp-up in weeks. Pick a service level. The tool gives the pre-build quantity that covers the gap, the extra safety stock caused by the longer lead time, and the value and holding cost of the total. Compare against the cost of a line stoppage or air freight to decide how much risk to carry. #### The math **Body:** Pre-build equals weekly demand times shutdown weeks, because the line consumes stock while no supply arrives. Safety stock follows the standard formula z times sigma times the square root of lead time. During the holiday window the lead time is longer, so the safety stock is higher. The extra safety stock is the difference between the two. Total extra inventory is pre-build plus that difference. **Bullets:** - Pre-build = weekly demand x shutdown weeks - Safety stock = z x sigma x sqrt(lead time weeks) - Holiday lead time = normal lead time + shutdown weeks #### Common mistakes **Body:** Ordering late is the usual failure. To receive stock before closure, orders must be placed one full lead time earlier, so planning starts in the autumn. Another mistake is covering only the public holiday and ignoring the slow return, or forgetting that sub-tier suppliers close too. In your ERP, load the shutdown as a supplier calendar so MRP shifts planned orders automatically, and review open purchase orders for due dates inside the closure. **Cta:** If you maintain supplier calendars and holiday overrides by hand, we can help automate calendar loading and flag at-risk purchase orders. **Faq:** #### How long should I assume the shutdown lasts? **Answer:** Ask each supplier. The statutory holiday is about a week, but many factories close longer and take weeks to regain full output. Three to five weeks of effective impact is a typical planning range. #### Why does safety stock increase? **Answer:** Safety stock grows with the square root of the exposure period. A longer effective lead time during the holiday window means more uncertainty over that period, so the buffer rises even if demand stays the same. #### Should I pre-build everything? **Answer:** Not necessarily. Focus on single-source, high-impact and long lead items. Cheap bulky parts may cost too much to hold, so compare holding cost with the cost of a stoppage item by item. #### Does it handle demand spikes before the holiday? **Answer:** No. If your customers also pull orders forward, raise the weekly demand or standard deviation to reflect it. The tool assumes steady demand with normal variation. ## Search terms chinese new year supply planning, spring festival safety stock calculator, china supplier shutdown buffer, pre holiday order quantity, lunar new year inventory planning, safety stock with lead time extension, china supplier lead time holiday, mrp buffer calculator --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json