Use the core calculator before paying.
- Single-product box comparison
- Copy recommendation summary
- US or metric input
- Light page ads
- CSV and preset libraries locked
Browser-based shipping decision tool
Small Seller Box Optimizer
Compare box choices before shipping so oversized packaging does not quietly eat your margin.
Recommendation
Medium Mailer Box
Below target
$15.66 estimated gross margin
Billable weight: 4 lb. DIM weight is higher than actual weight.
Shipping estimate
$5.40
Billable weight
4 lb
Margin rate
44.8%
Target sell price
$35.15
Length + girth
38 in
Margin lift
+$0.00
Compared with the next viable box.
Target gap
-$0.16
Current sell price versus the target margin price.
Risk review
DIM billed
Confirm final carrier rates before buying labels.
| Box | Fits | Status | Actual lb | DIM lb | Billable | Box cost | Ship est. | Margin | Target price | L+G |
|---|
Calculation assumptions
- DIM weight = length x width x height / 139. Box dimensions are rounded up before DIM weight is calculated.
- Billable weight = ceil(max(actual weight, DIM weight)).
- Shipping estimate = billable weight x $1.35 per lb.
- Length plus girth = longest side + 2 x width + 2 x height after billable dimensions are set.
- Gross margin subtracts product cost, handling cost, box cost, and estimated shipping from sell price.
- Target sell price estimates the price needed to reach a 45% gross margin.
Monthly and Annual workflow
Batch SKU comparison
Paste SKU rows to run the same box library and carrier assumptions across multiple products.
Columns: SKU, length, width, height, weight, sell price, product cost, handling cost. Use current input units and current box library.
| SKU | Best box | Status | Billable | Ship est. | Margin | Target price | Notes |
|---|
DIM Weight
Shows when a lightweight package is billed by space instead of scale weight. Read the DIM guide.
Margin Impact
Turns box size into estimated shipping cost and gross margin before listing. Read the margin guide.
Pricing Check
Shows the sell price needed to hit your target gross margin with each box. Read the pricing guide.
Editable Rules
Carrier divisors and rate assumptions stay editable because rules and accounts vary.
Monetization rule
Any paid pack makes the page ad-free
Free is for trust-building. One-time buys the permanent everyday calculator. Monthly and Annual buy the repeat seller workflow, starting with batch SKU comparison.
Permanent light-tool unlock for sellers who do not want a subscription.
- Page ads removed while payment remains valid
- CSV export
- Save multiple local box preset libraries
- Stays unlocked after one-time credits are used
- Does not include batch SKU workflow
For sellers who keep listing, testing, and changing packaging every month.
- Everything in One-time while active
- Batch SKU comparison from pasted CSV/TSV rows
- Local saved box preset libraries
- Fuller exports and repeat-use workflows
- Refund, dispute, or inactive status ends access
Monthly benefits for a full year at seven months of monthly pricing.
- All monthly paid features while active
- 12 months of access for the price of 7
- Ad-free pages, CSV export, and saved preset libraries
- Best fit for sellers already sure they will keep using it
- Refund, dispute, or inactive status ends access
Free access
Page ads are visible until a paid pack is connected.
FAQ
Does this replace a carrier quote?
No. Use it for packaging decisions, then confirm final rates inside UPS, FedEx, USPS, Pirate Ship, ShipStation, or your shipping account.
Are inputs stored?
The calculator runs in the browser. Current inputs are not sent to a server by this static version. Paid saved box preset libraries stay in this browser on this device.
Which features are paid?
Free users can compare boxes and copy the recommendation summary. Any paid pack unlocks CSV export, saved box preset libraries, and ad-free pages. Monthly and annual plans also unlock batch SKU comparison.
Can this help set a sell price?
Yes. Enter a target gross margin and the tool estimates the sell price each box option needs after product cost, handling cost, box cost, and estimated shipping.
Does a one-time pack remove ads?
Yes. One-time, monthly, and annual packs all remove page ads while their access state is active.
Why does the one-time pack not include batch comparison?
Because it is the permanent everyday calculator unlock: ad-free pages, CSV export, and local saved box preset libraries. Monthly and annual plans are for repeat sellers who need batch SKU comparison and larger ongoing workflows.
What happens after a refund or payment dispute?
Refunds, disputes, chargebacks, inactive payments, expired payments, or failed payments can end paid access immediately and restore the free page with ads.
Why are divisors editable?
DIM factors can vary by carrier, service, rate type, destination, and account contract. Editable assumptions keep the tool useful when rules change.
Where should I start if I am learning packaging math?
Start with the DIM weight guide, then read the shipping box margin guide and the free shipping price guide.