Lens Cap Size Guide: 40.5mm vs 62mm vs 72mm vs 77mm
By Borge's Imaging — Shop Photography, Printing and Studio Gear in Melbourne Borge's Imaging | Published: 2026-10-28
Category: Buying Guides
Find the right lens cap size for your lens. This guide compares 40.5mm, 62mm, 72mm, and 77mm Inca snap-on caps with decision rules and fit guidance.
Quick answer
Match the lens cap diameter exactly to the filter thread size printed on your lens barrel or lens cap. Inca snap-on caps in 40.5mm, 62mm, 72mm, and 77mm are affordable push-on options for common lens sizes.
Why diameter matters and what snap-on means
A lens cap that is too small will not stay on; one that is too large will not fit at all. The diameter you need is the same as the filter thread size, usually marked on the lens front ring or inside the cap. Inca snap-on caps use a clamp mechanism that pushes onto the lens barrel, so they do not require a threaded mount. This makes them quick to attach and remove, but the fit depends entirely on the cap's inner diameter matching your lens.
Trade-offs: no universal cap fits all lenses
Because each lens has a unique filter thread size, you cannot buy one cap for multiple lenses unless you use step-up rings. Inca snap-on caps are sold by exact diameter, so you need to know your lens size beforehand. If you own lenses with different thread sizes, you will need a separate cap for each. The benefit is that each cap is inexpensive and designed specifically for that diameter, providing a secure fit without the risk of cross-threading.
Decision rules for choosing your lens cap size
- Check your lens filter thread size: Look for a number like ⌀40.5, ⌀62, ⌀72, or ⌀77 printed on the front ring of the lens or inside the existing cap. That number is the exact diameter you need.
- Match the cap diameter exactly: Buy the Inca snap-on cap in that same diameter. For example, a 40.5mm lens requires a 40.5mm cap. Do not round up or down.
- Consider your lens collection: If you own multiple lenses with different thread sizes, purchase a separate cap for each. Inca caps are priced low enough that buying several is still affordable. Keep a spare cap for each lens you use regularly to avoid swapping.
Product facts
- Inca Lens Cap 40.5mm: 40.5mm Universal Lens Cap 'Snap' with clamp mechanism, push-on mount. Ideal for compact or vintage lenses with a small filter thread, such as some 50mm f/1.8 primes.
Inca Lens Cap 40.5mm - Inca Lens Cap 77mm: 77mm Universal Lens Cap 'Snap' with clamp mechanism, push-on mount. A common size for full-frame zoom lenses and telephoto primes; the larger diameter covers the front element securely.
Inca Lens Cap 77mm
Who should choose which size
Best for
- Photographers with a lens that has a filter thread of 40.5mm, 62mm, 72mm, or 77mm who want a low-cost snap-on cap
- Users who prefer a push-on cap over a pinch-style or threaded cap for quick protection
Not for
- Lenses with a filter thread size not listed here (e.g., 49mm, 52mm, 58mm, 67mm, 82mm, etc.)
- Photographers who need a single cap to fit multiple lens diameters without step-up rings
