Faraday bags come in standard sizes matching device categories: phone bags (6-9 inches) for smartphones and small items, tablet bags (10-13 inches) for iPads and similar devices, and laptop bags (13-17 inches) for notebooks. The key is buying a bag with 2-3 inches of extra room beyond your device dimensions to allow proper sealing – cramming a device into a barely-adequate bag prevents the closure from working correctly and can leave gaps that leak signals.
But here’s what most people get wrong: they buy bags that are too small, thinking a snug fit is better. A phone that barely fits into a 7-inch bag leaves no room for the roll-top closure or overlapping flap that actually creates the electromagnetic seal. You end up forcing the bag closed improperly, creating gaps where signals leak through. That extra space isn’t wasted – it’s essential for the bag to function.
Understanding sizing helps you avoid bags that physically fit your device but can’t seal properly, and prevents buying bags so oversized they’re awkward to carry or take up unnecessary space.
Quick Size Reference
Phone Bags (7-9 inches)
- Best for: All smartphones, key fobs, cards
- Add: 2 inches to phone height for sealing
- Example: iPhone 15 Pro Max (6.3″) → 8-9″ bag
Tablet Bags (10-13 inches)
- Best for: iPads, Android tablets, e-readers
- Add: 2-3 inches to tablet length
- Example: iPad Air (9.74″) → 12″ bag
Laptop Bags (13-17 inches)
- Best for: All laptops by screen size
- Add: 2-3 inches to physical length (not screen size)
- Example: MacBook Pro 16″ (14″ long) → 16-17″ bag
Key Principle: Always size up if between options. Too large works; too small doesn’t seal.
Standard Size Categories
Manufacturers typically offer bags in these standard ranges.
Different sizes serve different purposes, but all need the same fundamental signal blocking capability. For understanding what signals these bags need to block across all size categories, see what Faraday bags block.
Phone/Small (6-9 inches)
Designed for smartphones, key fobs, small accessories, and credit cards. Most modern smartphones fit comfortably in 7-9 inch bags with room for proper sealing.
iPhone 15 Pro Max (6.3 inches tall) fits well in 8-9 inch bags. Samsung Galaxy S24 Ultra (6.4 inches) similar. Even with cases, these devices work in standard phone bags with adequate sealing room.
Smaller phones or key fobs work fine in 6-7 inch bags, but there’s no reason to go smaller than necessary. The 8-9 inch range handles virtually all phones and provides flexibility.
Tablet/Medium (10-13 inches)
For iPads, Android tablets, e-readers, and small notebooks. Standard iPad (10.9 inches) and iPad Air (10.9-11 inches) fit 11-13 inch bags comfortably.
iPad Pro 12.9 inch models need the full 13-inch bag size. Smaller tablets like iPad Mini (8.3 inches) could use tablet bags but often fit better in larger phone bags (9 inches) with more sealing room.
E-readers like Kindle (6-7 inches) typically fit phone bags unless you prefer keeping them in tablet bags with other devices.
Laptop/Large (13-17 inches)
Laptop bags match standard screen sizes: 13-inch, 15-inch, and 17-inch categories. Measure your laptop’s actual dimensions including thickness to ensure proper fit.
13-inch MacBook Air (11.97 x 8.46 x 0.44 inches) fits 13-inch bags but needs the full width and depth. 15-inch laptops need 15-inch or larger bags. 17-inch gaming laptops require the largest bags available.
Consider laptop thickness too. Thin ultrabooks fit easily. Thick gaming laptops with ventilation need more internal depth.
Multi-Device/Extra Large (18+ inches)
Some manufacturers offer oversized bags for multiple devices or special equipment. These might accommodate laptop plus tablet, or professional equipment like cameras with phones.
Unless you specifically need to bag multiple devices together, standard sizes work better. Oversized bags are bulkier to carry and more awkward to seal properly.
Measuring Your Devices
Get accurate measurements before buying to ensure proper fit.
What to Measure
For phones and tablets, measure height (longest dimension), width, and thickness. Include any case you plan to keep on the device. Cases add 1-3mm typically, which matters for tight fits.
For laptops, measure length, width, and thickness at the thickest point (often the hinge area). Include any case or sleeve you want to keep on the laptop while bagged.
Don’t rely on manufacturer specs for “screen size.” A 15-inch laptop refers to diagonal screen measurement, not physical dimensions. Actual device dimensions vary significantly between models with the same screen size.
Adding Closure Room
Once you have device dimensions, add 2-3 inches to the longest dimension for proper closure room. A phone that’s 6.5 inches tall needs an 8.5-9 inch bag minimum for comfortable sealing.
Roll-top closures need 3-4 inches of extra material to fold properly (3-4 rolls). Overlapping flap closures need 2-3 inches. Even zipper closures with fold-over flaps need some extra room.
Bags that barely fit your device measurements cannot seal properly. The “extra” space is functional, not wasted.
Thickness Considerations
Flat devices like tablets and thin phones fit most bags easily regarding thickness. But thick smartphones with large cameras, rugged cases, or battery packs might not fit bags designed for standard phone thickness.
Check bag specifications for internal depth if your device is unusually thick. Gaming phones, rugged phones, or phones with PopSockets or similar accessories need extra clearance.
Phone Bag Sizing Specifics
Getting phone bag size right is critical since these are the most commonly purchased.
Small Phone Range (6-7 inches)
Older or compact phones like iPhone SE (5.45 inches), iPhone 13 Mini (5.18 inches), or similar Android devices fit these bags. Also good for key fobs, small accessories, or stacking multiple credit cards.
Most people should skip this size unless they have specific small devices. The medium phone range is more versatile.
Standard Phone Range (7-9 inches)
This handles virtually all modern smartphones including large models with cases. iPhone 15 Pro Max (6.3 inches) fits with 1-2 inches of sealing room. Samsung Galaxy S24 Ultra similar.
Buy 8-9 inch bags for maximum compatibility. Even if your current phone is smaller, future phones might be larger. The extra inch doesn’t make the bag significantly bulkier but provides useful flexibility.
Phone + Accessories (9-10 inches)
Some users want to bag phone plus wallet, keys, or earbuds together. Bags in the 9-10 inch range accommodate phone plus small accessories.
This is optional – you can use separate bags for different items. But single-bag convenience appeals to some users who want everything protected together.
Device Compatibility Examples
iPhone 15 Pro Max (6.33 x 3.02 x 0.32 inches): 8-9 inch bag Samsung Galaxy S24 Ultra (6.39 x 3.11 x 0.34 inches): 8-9 inch bag.
Google Pixel 8 Pro (6.4 x 3.0 x 0.35 inches): 8-9 inch bag iPhone 13 Mini (5.18 x 2.53 x 0.30 inches): 7-8 inch bag.
Add 0.5-1 inch if using thick cases.
Tablet Bag Sizing Specifics
Tablets have more size variation than phones, requiring careful sizing.
Small Tablet/Large Phone (9-10 inches)
iPad Mini (7.69 x 5.3 inches) technically fits 9-10 inch bags but sealing room is tight. These bags also work for large phones plus accessories or multiple phones.
This is a tweener size that bridges phone and tablet categories. Useful if you need something between standard phone bags and full tablet bags.
Standard Tablet Range (10-12 inches)
iPad (10.9 inch screen, 9.79 x 7.07 inches physical), iPad Air (10.9-11 inch screen, similar dimensions), and comparable Android tablets fit 11-12 inch bags comfortably.
This is the sweet spot for most tablet users. Provides adequate sealing room without excessive bulk.
Large Tablet Range (12-13 inches)
iPad Pro 12.9 inch (11.04 x 8.46 inches) requires the full 13-inch bag dimension. Some large Android tablets and 2-in-1 devices also need this size.
Check physical dimensions carefully – “12.9 inch” screen doesn’t mean the device is 12.9 inches in any dimension. Actual size is 11 inches tall, so 13-inch bags provide 2 inches of sealing room.
Tablet + Accessories (13-14 inches)
Some bags in this range accommodate tablet plus keyboard case, stylus, charging cables, or similar accessories. Useful for people who want to bag their complete tablet setup together.
Device Compatibility Examples
iPad Mini (7.69 x 5.3 inches): 10-11 inch bag iPad Air 11-inch (9.74 x 7.02 inches): 11-12 inch bag iPad Pro 12.9-inch (11.04 x 8.46 inches): 13-14 inch bag Samsung Galaxy Tab S9+ (11.22 x 7.28 inches): 12-13 inch bag
Laptop Bag Sizing Specifics
Laptop bags need precise sizing since laptops vary significantly in dimensions.
13-14 Inch Laptops
MacBook Air 13-inch (11.97 x 8.46 x 0.44 inches) needs a 13-inch bag minimum, 14-inch preferred for sealing room. Many Windows ultrabooks with 13-14 inch screens have similar dimensions.
These bags typically measure 14-15 inches internally to provide proper clearance. The “13-inch” designation refers to compatible laptop sizes, not bag dimensions.
15-16 Inch Laptops
This is the most common laptop size. Dell XPS 15, MacBook Pro 16-inch, HP Pavilion 15, and countless others fall here. Bag dimensions typically run 16-17 inches internally.
Width varies more than length in this category. Some 15-inch laptops are wider than others. Check both length and width specifications, not just screen size.
17 Inch and Larger
Gaming laptops, mobile workstations, and large business laptops. These often have significant thickness due to cooling requirements and high-performance components.
Bags in this range run 18-19 inches with extra depth for thick devices. These are the largest consumer Faraday bags readily available.
Thickness Matters More
Laptop bags need adequate depth for device thickness plus any case/sleeve you keep on the laptop. Measure at the thickest point (usually the hinge).
Gaming laptops might be 1-1.5 inches thick or more. Standard ultrabooks are 0.5-0.8 inches. The bag needs to close comfortably around the actual thickness.
Device Compatibility Examples
MacBook Air 13-inch (11.97 x 8.46 x 0.44 inches): 14-inch bag MacBook Pro 16-inch (14.01 x 9.77 x 0.66 inches): 16-17 inch bag Dell XPS 15 (13.57 x 9.06 x 0.71 inches): 15-16 inch bag Gaming laptop 17-inch (15-16 x 10-11 x 1-1.5 inches): 17-18 inch bag
When to Size Up vs Size Down
Choosing between sizes when you’re between standard categories.
Reasons to Size Up
Future devices might be larger. Phones and tablets trend toward larger screens over time. Buying a slightly larger bag now provides compatibility with future upgrades.
Multiple devices or accessories. If you might want to bag phone plus wallet, or tablet plus keyboard, the larger size provides flexibility.
Thick cases or ruggedized devices. Protective cases add significant bulk. Size up if you use heavy-duty protection.
Better sealing. More room means easier, more reliable closure. If you’re between sizes, the larger option ensures you can seal properly even when rushed.
Reasons to Size Down
Portability matters. Smaller bags fit pockets, purses, or small compartments better. If you’ll carry the bag daily, compact size has value.
Single specific device. If you only need to protect one device that you measured carefully, you can optimize for that exact size rather than building in extra flexibility.
Minimal extra room. Some closure types (especially sleeves) work fine with less extra space than roll-top designs.
When In Doubt, Size Up
It’s better to have a slightly larger bag that seals properly than a too-small bag that doesn’t close correctly. The size difference between adjacent categories is modest but the functionality difference is significant.
Multi-Device Considerations
Some situations require protecting multiple items simultaneously.
Separate Bags vs Combined
Separate bags for phone, tablet, and laptop provide flexibility. You can protect devices individually based on need rather than bagging everything together.
Combined protection in one larger bag is simpler when you want to isolate all electronics together. But it’s all-or-nothing – you can’t selectively access one device without exposing others.
Cost-wise, separate bags for each device type typically cost more total than one large bag. But the flexibility often justifies the extra cost.
Stacking Devices
If using one bag for multiple devices, stack them carefully. Hard items (laptops) on bottom, softer items (phones) on top. Avoid items with sharp edges or protruding cameras that might scratch other devices.
Some manufacturers make bags with internal separators or pockets that keep devices apart while maintaining electromagnetic isolation. These cost more but protect devices from physical damage while bagged together.
Size for the Largest
If bagging multiple devices in one bag, size for the largest device plus 2-3 inches for sealing. A laptop bag sized for your laptop will accommodate phone and tablet too, though they’ll be loose inside.
Use small pouches or sleeves inside the large bag to keep smaller devices from sliding around if desired. These internal organizers don’t need to be Faraday bags since the outer bag provides signal blocking.
The outer bag provides signal blocking through multi-layer construction that maintains electromagnetic shielding continuity. For detailed explanation of this construction, see how Faraday bags are made.
Specialized Sizing Needs
Some devices don’t fit standard categories.
Key Fobs
Most key fobs are 3-4 inches long. Dedicated key fob pouches run 4-6 inches, providing adequate room for the fob plus sealing space.
Key fobs also fit in small phone bags (6-7 inches) if you don’t need a dedicated pouch. The extra space doesn’t hurt functionality.
Credit Cards
RFID-blocking wallets come in standard wallet sizes matching regular bifold or trifold wallets. Dedicated card sleeves are roughly 4 x 3 inches (credit card size) with minimal extra room since sealing requirements are less demanding for thin items.
Cards also fit in phone bags if you want to protect cards and phone together.
Watches and Wearables
Smartwatches, fitness trackers, and similar devices typically fit phone bags. Most wearables are smaller than phones and don’t require dedicated sizes.
Some manufacturers make specific watch pouches 5-6 inches for users who want optimal sizing, but standard phone bags work fine.
Cameras and Electronics
Small cameras, portable game consoles, GPS devices, and miscellaneous electronics often fit tablet bags depending on dimensions. Measure carefully and add sealing room.
Professional camera equipment might need laptop-size bags or larger depending on size with lenses attached.
Closure Types and Size Requirements
Different closure mechanisms have different space requirements.
Roll-Top Closures
Need 3-4 inches of material beyond device size for proper rolling (3-4 complete rolls). A phone that’s 6 inches tall needs a 9-10 inch roll-top bag minimum.
This closure type requires the most extra room but provides excellent sealing through multiple overlapping layers.
Overlapping Flap Closures
Need 2-3 inches beyond device size for adequate flap overlap before Velcro engages. Less than roll-tops but still significant.
Zipper with Flap
Requires 1-2 inches beyond device size. The zipper provides structural closure, the flap provides electromagnetic sealing. Less extra room needed than roll-tops or flaps alone.
Sleeve Style
Slip-in sleeves with overlapping entrance need minimal extra room, maybe 1 inch. But these provide less secure sealing than closed pouches.
Match bag size to closure type. A roll-top bag needs more oversizing than a zippered bag for the same device.
Each closure type affects both sizing requirements and electromagnetic sealing effectiveness. For comprehensive details on closure mechanisms and seam construction, see how Faraday bags are made.
Real-World Size Selection Examples
Practical scenarios help illustrate sizing decisions.
Scenario 1: iPhone 15 Pro with Case
Device size: 6.3 x 3.0 inches plus 1mm case thickness Recommended bag: 8-9 inch phone bag with roll-top closure Reasoning: 2+ inches for roll-top sealing, accommodates case, provides margin for future larger phones
Scenario 2: iPad Air and Accessories
Device size: 9.74 x 7.02 inches plus Smart Keyboard case Recommended bag: 12-13 inch tablet bag Reasoning: Keyboard adds thickness and bulk, need room for both, 12-13 inches provides comfortable sealing space
Scenario 3: MacBook Pro 16 and Charger
Device size: 14.01 x 9.77 x 0.66 inches plus power adapter Recommended bag: 17-inch laptop bag Reasoning: Laptop needs 16-inch minimum, charger adds bulk, 17-inch provides room for both with sealing space
Scenario 4: Phone, Wallet, Keys Together
Devices: Phone (6.3 inches), wallet (4 inches), key fob (3 inches) Recommended bag: 9-10 inch phone bag or small tablet bag Reasoning: Stacking multiple items needs extra room, 9-10 inches accommodates everything with sealing space
Scenario 5: Multiple Phones (Family Travel)
Devices: 3-4 smartphones ranging 5.5-6.5 inches Recommended bag: 12-inch tablet bag Reasoning: Stacking multiple phones needs tablet-size bag, allows grouping family devices for easy handling
Common Sizing Mistakes
Understanding errors helps avoid them.
Buying Too Small
Most common mistake. Device dimensions plus zero sealing room means bag can’t close properly. Signals leak through gaps created by forced closure.
Always add 2-3 inches minimum to device size. More for roll-top closures.
Assuming Screen Size Equals Bag Size
A 13-inch laptop screen doesn’t mean a 13-inch bag fits it. Physical dimensions differ from screen measurements. Always check actual device dimensions.
Ignoring Thickness
Length and width fit, but thick devices don’t. Especially problematic with gaming laptops, rugged phones, or devices with bulky cases.
Measure thickness at thickest point and verify bag has adequate depth.
Not Testing Closure
Bag dimensions look adequate on paper but trying to actually close it reveals it’s too small. Physical testing shows whether you can seal properly.
If possible, test closure with device before committing. If buying online, verify return policy allows testing.
Forgetting About Cases
Measuring naked device but keeping case on in actual use. Cases add 2-5mm typically, which matters for tight fits.
Measure with case on if you’ll bag the device with case.
Size and Performance Relationship
Bag size affects more than just fit.
Larger Bags, Easier Sealing
More room means easier, more reliable closure. You’re not fighting tight fits or forcing closures. This improves real-world blocking performance.
Slightly oversized bags seal better than perfectly sized bags, assuming closure is done properly.
Size Doesn’t Affect Shielding
A 9-inch phone bag and 17-inch laptop bag with the same construction provide identical signal blocking per square inch. Size affects convenience and closure ease, not inherent shielding capability.
Buy based on device fit and closure requirements, not assuming larger bags block better.
Portability Trade-offs
Larger bags are bulkier to carry but easier to seal. Smaller bags are more portable but require more careful closure.
Balance convenience against reliability based on how you’ll actually use the bag.
Getting It Right
Choosing correct Faraday bag size prevents functional problems and wasted money. Measure your devices accurately including any cases or accessories. Add 2-3 inches to the longest dimension for proper sealing room. Match bag size to closure type requirements – roll-tops need more extra room than zippers.
When between sizes, err toward larger. A slightly oversized bag that seals properly outperforms a perfectly sized bag that barely closes. The extra room is functional, not wasted space.
For comprehensive guidance on choosing the right bag beyond just size, see our complete buying guide. To understand construction quality differences, read our layer comparison guide.
Buy from sellers with clear size specifications and good return policies. Test closure with your actual devices within the return window. If the bag doesn’t seal comfortably with your device inside, return it and size up.
Standard sizing (phone 7-9 inches, tablet 10-13 inches, laptop 13-17 inches) covers most needs. Measure carefully, add sealing room, and choose the next size up if uncertain. That approach gets you bags that actually work rather than bags that technically fit but can’t seal properly.