Approach inventory planning correctly: Inventory Planning on Shopify (Guide)

Inventory planning is one of those topics rarely discussed in e-commerce. Yet it's one of the key factors determining whether a brand can grow profitably in the long term. After all, even the best marketing campaign is worthless if the product isn't available at the end.

In the tante-e podcast with Johannes Gassner, Head of Growth at fabrikatör, we take a practical look at the importance of inventory planning for modern e-commerce brands. We summarize the key insights on inventory planning for Shopify retailers in this article.

1. What is inventory planning – and why is it so crucial?

Inventory planning is more than just deciding which products to order and when. It's the connection between marketing, finance, and purchasing—and thus a key control tool for profitable growth in e-commerce.

Johannes describes inventory planning as the balancing of what a company wants to sell ( demand ) with what it can actually deliver ( supply ). The goal is to achieve the greatest possible impact with limited capital – without excess inventory or out-of-stock situations.

Inventory planning essentially comprises three levels:

level	focus	Goal
Demand Planning	Marketing planning, expected demand, external factors	What do we want to sell – and what is realistic?
Supply Planning	Inventory, suppliers, production capacities, lead times	What can we deliver – and under what conditions?
Alignment & Control	Financial resources, timing, seasonal factors	What is feasible – without losing liquidity?

A typical example from everyday life: A brand is planning a campaign for January. It expects high demand because January is historically a strong sales month, for example, for sports or wellness products. If too little inventory is planned for this time, there is a risk of out-of-stock . If too much inventory is purchased, in the worst case scenario, there will be insufficient budget for the campaign itself.

The central challenge:
In e-commerce, capital tied up in inventory is a relevant factor. Overbuying blocks liquidity; underbuying loses revenue. This becomes particularly problematic when the forecast isn't based on solid data.

Inventory planning is therefore not an operational detail, but a strategic lever . Brands that take this discipline seriously early on gain a decisive advantage.

2. Typical mistakes and pitfalls – and how to avoid them

Despite its central importance, inventory planning is neglected in many e-commerce companies – often with serious consequences. In the podcast, Johannes speaks openly about recurring patterns he's observed in his work with over 200 brands. The most common mistakes at a glance:

2.1. Planning based on gut feeling rather than data

Many companies order products "as they feel right" – without any concrete analysis or forecasting. This works until the initial growth phase is over or external factors influence demand.

2.2. Out-of-stock is accepted

An out-of-stock rate of 30–40% is "business as usual" in some companies. The problem: The brand not only loses sales but also customer trust—while wasting marketing budget.

2.3. Capital tied up by excess inventory

Keeping too much in stock ties up liquidity that's missing elsewhere, such as in marketing or product development. This is especially dangerous for seasonal products or fashion items, whose relevance can quickly decline.

2.4. No differentiated analysis of the warehouse data

Without a breakdown by category, sales channel, or time period, it's difficult to understand which products are truly important. Johannes cites ABC analysis as a key method here:

category	Share of sales	Recommendation for action
A-products	~80%	Always keep it available – highest priority
B-products	~15%	Stock up as needed, use upsell
C-products	~5%	Reduce stocks, rethink product range

2.5. Neglecting the turnover rate and cash cycles

A product that sits in inventory for three months blocks capital—even if it eventually sells. Products with high inventory turnover are better: They turn over faster and generate more profit in a shorter time.

What helps instead:

• Establish monitoring & tracking as a mandatory task
• Systematically evaluate seasonality (e.g. with multi-year sales data)
• Targeted communication with suppliers to enable buffers or pre-production
• Consistent KPI evaluation with a focus on margins, demand distribution and availability

3. Inventory Planning in Practice – How Shopify Brands Are Approaching the Topic Today

What does inventory planning look like in the everyday life of e-commerce brands? In this interview, Johannes Gassner shares insights into fabrikatör's collaboration with brands that are systematically working on their inventory planning today.

3.1 The first step: honest assessment

The process often begins with a simple question: "How are you currently doing this?" Because planning is never completely successful—someone is always making decisions. Whether consciously or subconsciously, whether data-based or gut-motivated. Johannes emphasizes:

This is followed by three key steps:

3.2.. Create data structure

Sales data, returns, delivery times, supplier information, marketing forecasts: All of this data is often distributed across different tools and formats. The goal is to consolidate it into a unified structure. This is the only way to make reliable analyses and decisions.

3.3.. Identify influencing factors

What factors drive demand? Seasonality, weather, marketing campaigns, influencer spikes – all of these influence how many products are needed. Johannes describes it as a kind of "wallpaper" on which various data sources are compiled, evaluated, and forecasts derived.

3.4. Test forecasts and improve them iteratively

No forecast is perfect. The key is to systematically document assumptions, compare them with reality, and learn from them. Why were we wrong? What was overlooked? Where is a missing data point? This is how a robust model is created step by step.

Practical example: A Finnish shoe brand

A brand with multiple sales channels—online shop and brick-and-mortar stores—was struggling with out-of-stock issues throughout the year. The result: internal disputes over order quantities, missed sales, and unclear responsibilities.

Fabrikatör supported the brand with the following measures:

• Consolidation of data from all channels
• Creation of a uniform database
• Conducting ABC and XYZ analyses to prioritize products
• Identification of seasonal patterns, e.g., for certain colors or models
• Introduction of backorder functionalities to reduce lost revenue

The result:

• Out-of-stock rate was reduced by 50% in just a few months
• Sales losses due to pre-orders (backorders) significantly reduced
• Clarity within the team regarding priorities and ordering decisions

Inventory planning thus shifts from reactive mode to creative mode, enabling brands to steer their operations rather than improvise. This transition is particularly crucial when product ranges are growing and multiple sales channels are used.

4. Recommendations for action: How to approach inventory planning in a structured manner

The theory is understandable—but how do you actually implement inventory planning? Johannes shares a clear approach that has proven successful for many brands. The key: a structured approach, a pragmatic approach, and continuous improvement.

Four steps to get started with inventory planning:

1. Record the status quo

• Which systems do you currently use? (ERP, Shopify, Excel, etc.)
• How are orders planned and executed today?
• Which pain points in the warehouse or supply chain are known?

Goal: Create transparency about processes, responsibilities and weak points.

2. Identify and standardize data sources

Relevant data sources:

• Sales channels (e.g. Shopify, Amazon, POS)
• Returns and warehouse data
• Delivery times and production capacities
• Marketing plans and planned campaigns

Important: Bring all data into a uniform format so that it can be compared and analyzed.

3. Build a forecasting model

Identify influencing factors:

• Seasonal patterns
• Weather, events, external factors
• Marketing measures (performance, influencers, drops)

Treat forecasts as hypotheses, document them, and compare them with real data. Transfer insights to subsequent cycles – forecasting improves with each iteration.

4. Act based on data & continuously optimize

• Regular reviews: What went well? Where did we go wrong?
• Strengthen collaboration between purchasing, marketing and finance
• Use analyses in a targeted manner: e.g., ABC analysis for prioritization, turnover ratio for capital commitment

5. Additional leverage: Introduce backorders

Backorders—the ability to pre-order sold-out products—not only help reduce lost revenue but also improve liquidity. According to experts, in many cases, this has been able to offset 50–70% of potential revenue losses—without additional advertising costs.

What is important:

• Communicate expectations clearly (delivery times, status updates)
• Automate processes (e.g. via Shopify and Klaviyo)
• Prioritize customer experience (e.g., through real-time information and proactive communication)

Inventory planning is not a one-time measure, but a continuous process.
Those who implement it consistently create the basis for reliable decisions, efficient use of capital – and ultimately: more sales with less risk.

5. Inventory Planning Tools for Shopify: When Excel is enough – and when it isn’t

Many Shopify brands start their inventory planning with Excel – and that's perfectly legitimate. According to Johannes, there are companies with seven-figure sales that still plan using manual spreadsheets. What's often underestimated is that the effort increases with complexity. More products, more channels, more suppliers – and suddenly teams are spending days or even weeks updating forecasts.

The limitations of Excel:

• Susceptibility to errors due to manual entries
• No automatic data integration from systems such as Shopify, ERP or marketplaces
• No history, no scenarios, no automated alerts
• Difficult collaboration between multiple stakeholders (e.g. marketing, finance, operations)

A modern tool like fabrikatör comes in right here:

function	Advantage for inventory planning
Automatic data connection	Integration with Shopify, marketplaces & ERP – no manual exports required
Over 150 KPIs & analyses	Direct insights into out-of-stock rates, turnover, forecast deviations, etc.
Backorder functionality	Continue selling products despite out-of-stock, including automated communication
Klaviyo integration	Targeted updates in case of delays or changes in delivery status
Forecasting with experts	“Inventory Analyst on Demand” – individual support without your own in-house team

The insight:
The more sales channels and products a brand has, the more urgently it needs a system that reduces complexity—not increases it. Tools help Shopify merchants stay on top of things, make data-driven decisions, and act faster. And that's exactly what makes the difference in the end.

6. Conclusion: The most important learnings about inventory planning

6.1 Planning is teamwork
Inventory doesn't just affect the warehouse or purchasing department. It requires the collaboration of marketing, finance, and operations – based on a common data foundation.

6.2. No reliable forecast without clean data
Whether using Excel or a specialized tool, if you don't know how products are developing, you can't manage them effectively. Analyses such as ABC/XYZ classifications, turnover ratios, or lost revenue forecasts provide the necessary foundation.

6.3 Complexity increases with growth
More products, more channels, more markets – what initially works with feeling and tables eventually requires clear processes, structured data and supporting tools.

6.4. Backorders are a simple, effective lever
They reduce lost sales, improve planning for suppliers and help secure liquidity – provided that communication and expectation management are well set up.

6.5. Inventory planning is not a purely operational issue, but an important strategic factor. Those who invest specifically in data structure, forecasting, and systematization today lay the foundation for sustainable growth, more satisfied customers, and better margins.