Quick Answer: Measure the longest, widest and tallest points of your item, including handles, knobs and cables. Then add room for foam on every side and on top. Tell your manufacturer whether your numbers are inside or outside sizes. Most fitting problems come from skipping one of those three things.
A case that is 1 cm too small is useless. A case that is 5 cm too big lets your gear move around, and that is how things break in transit. Here is how we size cases with our customers, step by step.
Step 1: Gather Everything That Goes in the Case
Lay out the main item and every extra: chargers, cables, batteries, remote controls, lens caps, manuals. Buyers often measure only the main product, then find the charger has nowhere to go.
Decide now what must travel in the case and what can stay behind.
Step 2: Measure the Longest Points, Not the Body
Use a hard tape measure or calipers, not a sewing tape. Measure:
- Length: the longest side, end to end.
- Width: the widest point, including handles or side knobs.
- Height: the tallest point, including buttons, antennas or feet.
Write each number in millimeters if you can. Round up, never down.
Step 3: Add Room for Foam
Foam is what protects your item, so it needs space. As a starting point, many buyers allow:
- 2–3 cm of foam on each side of the item.
- 2–3 cm of foam under it.
- 2–3 cm of lid foam above it.
Heavy or very fragile items may need more. Light items in a snug die-cut insert may need less. Your manufacturer should confirm this for your product.
Step 4: Work Out the Inside Size of the Case
Inside Length = Item length + foam on both sides
Inside Width = Item width + foam on both sides
Inside Depth = Item height + foam below + lid foam above
Worked Example: A drone measures 300 × 250 × 100 mm. With 30 mm of foam on each side, below and above:
| Item | Foam Added | Inside Case Size |
|---|---|---|
| Length | 300 mm + 30 + 30 mm | 360 mm |
| Width | 250 mm + 30 + 30 mm | 310 mm |
| Depth | 100 mm + 30 below + 30 lid | 160 mm |
If the remote and batteries also go in, add their space beside the drone before you add the foam.
Step 5: Say Clearly If You Mean Inside or Outside Size
The frame, panels and lid of an aluminum case add to the outside size. So a case with an inside size of 360 × 310 × 160 mm will be bigger on the outside.
This matters for two reasons:
- Inside size decides whether your item fits.
- Outside size decides whether the case fits on a shelf, in a vehicle or in airline carry-on limits.
When you send your numbers, write “inside” or “outside” next to them. It avoids the most common mix-up we see.
Mistakes That Cost Buyers a Second Sample
- Measuring without the handle or knobs. The item fits on paper but not in the foam.
- Forgetting cables and chargers. There’s no cut-out for them, so they get squeezed in and press on the item.
- Rounding down. A 1–2 mm squeeze in hard foam is enough to make an item hard to take out.
- Not checking the weight. A 15 kg item needs stronger hinges, handles and corners than a 2 kg one. Always send the weight too.
- Mixing inches and centimeters. Pick one unit and stick to it.
When to Send the Actual Product
For custom die-cut or CNC-cut foam, numbers alone are sometimes not enough. Curved or odd-shaped items are hard to describe on paper. In those cases, we may ask you to send one unit to our factory in Foshan. That way the foam is cut to the real shape and checked before mass production.
Frequently Asked Questions
How much space should I leave around my item in a case?
A common starting point is 2–3 cm of foam on every side, below and above. Heavier or more fragile items usually need more. The manufacturer should confirm the final number for your product.
Should I give the inside or the outside size?
Give the inside size if fit is your main concern. Give the outside size if the case must fit a fixed space, like a shelf or carry-on limit. Always label which one you mean.
Can MSACase work from a drawing instead of the product?
Yes. A CAD drawing or a dimensioned sketch works well for simple shapes. For complex shapes, a physical sample gives the most accurate foam fit.
What if my measurements are slightly off?
That’s what the sample stage is for. You check the sample case with your real item before the bulk order starts.
Ready to Size Your Case?
Send us your item’s length, width, height and weight, plus a photo with a tape measure. Our team will suggest the right inside size and foam layout.