Free shipping, flat-rate shipping and calculated shipping solve different problems. The right choice depends on margin, order-value distribution, package variability and how much shipping-cost volatility your business can absorb.
Free shipping
Free shipping can simplify checkout, but the cost still exists. It must be absorbed in product margin, built into prices or limited with a threshold. Before offering it broadly, calculate your average shipping-and-packaging cost per order and identify expensive outliers.
Use the Packaging Cost Calculator together with the shipping cost per order framework.
Flat-rate shipping
A flat fee is easy to communicate and can work well when most orders have similar size, weight and destination mix. It becomes risky when a few bulky or remote-zone orders cost far more than the average.
Calculated shipping
Calculated rates shift more cost variability to the buyer and can protect margin, but the checkout total may be less predictable. Accuracy depends on correct packed dimensions and weight. If catalog dimensions are wrong, calculated shipping can still undercharge or overcharge.
A practical hybrid
Many merchants use free shipping above a threshold, a flat fee below it and exclusions for unusually large items. Test the threshold against real order economics rather than copying a competitor.
Packaging affects all three models
Lower dimensional weight reduces the cost you absorb under free shipping, reduces the risk embedded in a flat rate and improves calculated-rate outcomes. Use the Box Size Optimizer for high-volume SKUs.
Shopify’s own shipping guidance emphasizes building a shipping strategy around customer expectations and business economics rather than treating one model as universally best; see Shopify’s shipping strategy resources.
Free vs flat vs calculated: operating tradeoffs
| Model | Main advantage | Main risk | Best fit |
|---|---|---|---|
| Free shipping | Simple customer proposition | Merchant absorbs cost variation | Healthy margins and predictable order economics |
| Flat rate | Predictable checkout charge | Expensive outliers can be underpriced | Relatively consistent package/destination mix |
| Calculated | Cost follows shipment profile | Higher or volatile checkout price | Variable sizes, weights or destinations |
How to model a free-shipping threshold
Assume an average order value of $55, contribution before shipping of $22 and average shipping-and-pack cost of $9. Offering free shipping on every order leaves $13 before other variable costs. A threshold can make sense if larger baskets create enough incremental margin to cover the absorbed shipping cost.
Do not choose a threshold only because a competitor uses it. Analyze order-value distribution, contribution margin and the actual shipping cost per order.
Where flat rates fail
Flat rates are most vulnerable when a minority of orders are bulky, remote or unusually heavy. Before choosing one price, segment historic orders by zone and package family. If the spread is wide, use exclusions, tiers or calculated rates for the outliers.
Frequently asked questions
Does free shipping actually mean free?
No. The shipping cost is absorbed by the merchant, built into product pricing, recovered through a threshold or offset elsewhere in the economics.
Can I combine the three models?
Yes. A common structure is free shipping above a threshold, a flat rate for ordinary orders below it and calculated or special handling for oversized items.
Should packaging be part of the threshold calculation?
Yes. Packaging and packing labor are real variable costs. Use the Packaging Cost Calculator to avoid understating them.
When should I revisit my shipping policy?
After meaningful carrier-rate changes, packaging changes, margin shifts or changes in destination mix.
Related guides
PackToolbox guides are built around stated formulas, practical examples and source checks for changeable carrier, freight and logistics rules. Calculators are planning aids; final requirements should be verified with the relevant carrier or service provider.