3PL vs Self-Fulfilment: When to Outsource Your Warehouse and When to Keep It In-House

The true cost of self-fulfilment#

Self-fulfilment appears cheaper on a variable cost basis — you pay for labour and materials per order rather than a 3PL's pick, pack, and ship fee. But the full cost of self-fulfilment includes fixed costs that are often not properly attributed: warehouse rent or the opportunity cost of the space, warehouse equipment (racking, pallet trucks, scales, printers), packaging materials in bulk (which require capital), utilities and insurance, and most critically the management time of the founder or a dedicated operations person. When these fixed costs are included and spread across order volume, self-fulfilment is often more expensive per order than a 3PL below volumes of 200-400 orders per month.

What a 3PL charges and how to compare#

3PL pricing typically includes receiving fees (per pallet or per unit received into the warehouse), storage fees (per pallet per week or per cubic metre per month), pick and pack fees (per order plus per item — typically £1.50-3.50 per order for standard eCommerce), shipping cost (typically at negotiated carrier rates), returns processing (per return), and account management fees (monthly minimum or fixed fee). To compare to self-fulfilment, calculate your total 3PL cost per order at your current volume — including all fee components — and compare this to your self-fulfilment cost per order including the full fixed cost allocation.

The break-even volume calculation#

The break-even volume is where total 3PL cost equals total self-fulfilment cost. Self-fulfilment total cost = Fixed costs (rent, equipment, management) + Variable costs (labour per order × orders + materials per order × orders). 3PL total cost = Fixed minimum fees + Variable fees per order × orders. Plot both as functions of monthly order volume. The intersection is the break-even point. Below this volume, 3PL is cheaper (fixed cost advantage). Above this volume, self-fulfilment becomes cheaper (variable cost advantage). For most businesses, this break-even is between 300-800 orders per month depending on the specifics.

Beyond the numbers: the non-financial case for 3PL#

Even when self-fulfilment is cheaper per order, the non-financial case for 3PL is often compelling. Time: founders who self-fulfil often spend 20-30% of their working week on warehouse and fulfilment operations — time that could be spent on product development, marketing, or sales. Scalability: a 3PL can absorb a 5x volume spike without any action from you; a self-fulfilment operation requires emergency staffing and space. Geographic flexibility: a 3PL in a strategic location can reach more of your customer base within next-day delivery SLA. International expansion: 3PLs with international networks enable export fulfilment without establishing your own overseas warehouse.

Evaluating 3PL providers: what to look for#

Not all 3PLs are equal. Evaluate on: eCommerce specialisation (do they have experience with your type of inventory and order profile — high SKU count, fragile goods, returns handling), system integration (does their WMS integrate directly with your Shopify, Amazon, or other platform — manual data entry creates errors and delays), location (proximity to your customer base and ports for inbound goods), and pricing transparency (do they provide clear per-unit pricing without hidden fees). Visit the facility before committing — the quality of warehouse management is visible in person in a way it is not in a pricing proposal.