Start with the right AOV, delivery cost and gross margin
Use a recent, representative period for average order value (AOV): merchandise revenue after discounts and before tax divided by orders. If a few unusually large orders distort the mean, inspect the median and the distribution of cart subtotals too. A threshold that most shoppers cannot reach with one sensible add-on may create friction even when its unit economics look safe.
Enter the shipping and handling amount your store would actually absorb for a qualifying order. Use a weighted average for the shipping zones and package sizes likely to qualify, then recheck remote-zone and heavy-basket exceptions. Gross margin is the share of merchandise revenue left after product cost, before shipping, advertising, payment processing and overhead. Keep all monetary inputs in USD on this page.
The free shipping threshold formula and its two floors
The target-lift basket equals AOV × (1 + target lift %). The shipping-offset floor equals AOV + average shipping cost ÷ gross margin as a decimal. The recommended free shipping minimum is the larger of those two amounts, rounded up to a whole dollar. The second floor answers a specific question: how large must the order become so its additional product gross profit covers the shipping subsidy? It is stricter than merely asking whether the order stays above zero after shipping.
For example, at $60 AOV, $8 shipping cost, 40% gross margin and a 20% target lift, the target-lift basket is $72. Incremental gross profit on that $12 lift is only $4.80, below the $8 shipping bill. The shipping-offset floor is $60 + $8 ÷ 0.40 = $80, so the tool recommends $80. At that amount, product gross profit is $32; after the $8 shipping subsidy, $24 remains—the same gross-profit dollars as a $60 order before merchant-funded shipping.
Read the margin impact alongside the dollar result
After-shipping contribution at the threshold equals threshold × gross margin − shipping cost. The displayed after-shipping margin divides that contribution by the threshold. Margin impact compares it with your input gross-margin rate in percentage points. In the $80 example, $24 ÷ $80 = 30% after-shipping margin, which is 10 percentage points below the original 40% product gross margin, even though the order preserves $24 in gross-profit dollars.
A lower percentage margin is expected when you absorb delivery. The more relevant guardrail for this model is whether the added basket gross profit offsets the new shipping expense. The comparison assumes today’s AOV order does not already include a merchant-funded shipping subsidy. If you currently offer free shipping at all order values, the baseline must be adjusted; use the outputs as a scenario rather than a before-and-after forecast. “After-shipping” also excludes payment fees, ads, returns, taxes and fixed overhead, so it is not accounting net profit.
A practical Shopify setup and cart message
In Shopify, create a price-based free shipping rate in Settings → Shipping and delivery for the relevant shipping profile and zone. Match the rate’s minimum order price to the threshold you choose. Check whether the rate applies to the cart subtotal you use in the banner after discounts and how your theme displays tax and shipping; inconsistent bases produce misleading “amount left” messages.
The preview uses your example cart subtotal, or the entered AOV when that field is blank. For a real storefront, replace it with the live qualifying cart subtotal and recalculate the remaining amount as max(0, threshold − cart subtotal). Place the message where shoppers choose products and in the cart, not only in a sitewide header. Suggest relevant add-ons near the threshold; do not push a filler item whose own margin or added weight defeats the economics.
Why this tool cannot identify the conversion-maximizing number
Conversion response depends on actual cart-value distribution, product prices, repeat purchase behavior, shipping expectations and competitor offers. None of those outcomes is determined by AOV, delivery cost and gross margin alone. A mathematically safe floor may be too high for customers to reach, while a lower threshold may be worthwhile if extra conversions compensate for thinner profit per qualifying order.
Use the recommendation as a first candidate, then compare a few nearby thresholds in a controlled test. Track checkout conversion, AOV, the share of orders qualifying for free shipping, total delivery subsidy and contribution profit per visitor. Segment new versus returning customers and shipping zones where possible. A threshold is working only when the observed overall contribution improves; the calculator cannot prove that from four inputs.
Check the assumptions that can change the answer
The formula uses one average gross margin. If customers add a discounted or low-margin product to unlock shipping, the incremental margin may be much lower. Larger baskets can also trigger higher weight-based shipping charges. Recalculate with the margin and shipping cost of the likely qualifying basket, and consider exclusions or a different rate for bulky items or costly delivery zones.
Payment processing, packaging, returns, taxes, cross-border duties and acquisition cost are outside this simple shipping model. If your current policy charges a shipping fee to customers, the fee may also affect current order contribution; if shipping is already free below the proposed threshold, incremental shipping economics differ. Record your baseline policy and validate the offer with actual order-level data before rolling it out broadly.