Which Lens Cap Size Do You Need? 55mm vs 72mm vs 77mm
By Nelson Photo & Video | Published: 2026-10-29
Category: Buying Guides
Find the right lens cap size by checking your lens filter thread. Compare 55mm, 72mm, and 77mm snap-on options and choose the best fit for your gear.
Quick answer
The correct lens cap size is the same as your lens filter thread diameter (marked on the lens barrel or under the cap). For common diameters, the Promaster 55mm, 72mm, and 77mm Professional Lens Caps offer a secure, center‑locking fit at a budget‑friendly price, while the Nikon LC‑77 provides genuine brand compatibility for Nikon shooters.
Why size matters
A lens cap that’s too small won’t stay on; one that’s too large won’t attach at all. Each lens has a specific front filter thread diameter measured in millimeters—this number determines which cap fits. Using the wrong size can leave your front element exposed to dust, scratches, and accidental damage.
How to find your lens cap size
Look on the front of your lens barrel for a symbol like “⌀” followed by a number (e.g., ⌀55, ⌀72, ⌀77). That’s your filter thread size and the cap size you need. If you can’t find it, check the underside of your current cap or the lens manual. A common mistake is confusing the lens model number with the thread size—they are not the same.
Decision rules for choosing your lens cap size
- Check the filter thread mark: Look for the “⌀” symbol on the front of your lens. That number (e.g., 55, 72, 77) is the exact cap size you need. If you see “⌀72”, get a 72mm cap.
- Match the cap to your most‑used lens: If you have multiple lenses with different thread sizes, buy a dedicated cap for each. Sharing a cap between lenses risks losing it or forcing a wrong fit. Consider a cap leash (like the ones sold at Nelson Photo & Video) to keep each cap attached to its lens.
- Choose between OEM and third‑party: Genuine caps like the Nikon LC‑77 offer perfect fit and brand consistency but cost more. Third‑party caps like the Promaster Professional series provide a secure center‑locking mechanism at a lower price—ideal for replacements or spare caps.
Product facts
- Promaster Snap-on Front Lens Cap - 77mm: Promaster Snap‑on Front Lens Cap – 77mm uses a center‑activated locking system for a secure fit. The center‑lock design lets you attach and remove the cap quickly without touching the lens barrel, reducing the risk of fingerprints or accidental shifts.
Promaster Snap-on Front Lens Cap - 77mm - Nikon LC-77 Snap-on Front Lens Cap 77mm: Nikon LC‑77 Snap‑on Front Lens Cap 77mm is a genuine Nikon accessory engineered for lenses with a 77mm filter thread. If you prefer OEM parts, the LC‑77 guarantees exact tolerances and a reliable snap‑on action, though it costs more than third‑party alternatives.
Nikon LC-77 Snap-on Front Lens Cap 77mm
Which cap is right for you?
Best for
- Photographers who want an affordable, secure replacement cap for a 55mm, 72mm, or 77mm lens – choose the Promaster Professional Lens Cap in your size.
- Nikon users who prefer genuine OEM accessories for their 77mm lens – the Nikon LC‑77 offers a precise snap‑on fit.
Not for
- Lenses with a non‑standard filter thread size (e.g., 58mm, 62mm, 67mm) – these caps only fit 55mm, 72mm, and 77mm threads.
- Lens caps that need to be locked or tethered – consider adding a cap leash for security.
