BR30 vs. BR40 Bulbs: Size, Fit and Light Checks

BR40 Is Wider; It Is Not a Universal Upgrade

BR30 means a nominal maximum diameter of 30 eighths of an inch (3.75 in); BR40 means 40 eighths (5.00 in). That difference can affect whether the lamp clears a trim or obstruction and how it looks at the ceiling. It does not establish that a BR40 is brighter, has a wider beam, fits every “6-inch can,” or can replace a BR30 safely.

Start with the old lamp’s full marking and the fixture documentation. Then compare the exact replacement’s diameter and length, base and voltage, dimmer or control requirements, thermal or enclosed-fixture limits, and dry/damp/wet-location language. Only after that should you compare delivered lumens, CCT/CRI, and distribution or beam data.

The BR Number Names the Bulb Diameter, Not the Ceiling Opening

In this lamp nomenclature, the number is expressed in eighths of an inch: 30 ÷ 8 = 3.75 in and 40 ÷ 8 = 5.00 in. Those are nominal maximum bulb diameters. Product records can use a slightly different actual diameter, and they list length separately.

A “4-inch” or “6-inch” recessed fixture can refer to a housing, aperture, trim, or cutout convention. It does not convert directly to a BR lamp designation. Use the exact fixture’s documentation and the recessed-light measurement sequence to record the opening, trim, body and accessible space separately.

Can I Replace a BR30 With a BR40?

Sometimes, but only when the proposed BR40 is documented to work in the existing fixture and the larger actual lamp envelope clears the trim and nearby parts. The shared E26 medium base on many examples only addresses the socket interface; it does not prove fixture, thermal, dimmer, location, or optical compatibility.

If the fixture is an integrated LED module rather than a replaceable screw-base lamp, this comparison is not the replacement path. Identify the complete assembly first; see how to identify and change a replaceable recessed bulb and the spec-sheet guide for the fields that must match.

Two Manufacturer Product Records Show Why SKU Data Matters

These selected LEDVANCE / SYLVANIA records are concrete examples, not a claim that all BR30s or BR40s share their output, size, beam, or location characteristics. Their beam values are shown as “Not reported” because the cited product records do not report beam angle; that is not a zero-degree beam.

The two records have different output and power values, but those values belong to these models—not to the BR number by itself. Their actual diameters also illustrate why the naming convention and a product’s stated dimensions should both be checked.

Choose by Your Existing Fixture and the Light You Need

Choose the lamp that the existing fixture can accept and that has a verified physical envelope. Then select light using the product’s stated lumens, color setting, color rendering, and distribution information. A larger BR label does not replace either check.

Ready to shortlist a bulb? Keep an exact SKU as a purchase candidate only when the fixture instructions permit its lamp type, its actual diameter and length clear the trim and obstructions, and the voltage, location, enclosure and control conditions match. If any check is unresolved, get the missing product documentation before ordering.

The calculator estimates a general-lighting count and layout from disclosed inputs. It does not identify a lamp, approve a substitution, validate fixture ratings, or create missing optical data.

Sources and Scope

Maintained by Recessed Light Calculator. This is a lamp-nomenclature and product-check guide, not a fixture test, installation instruction, or universal compatibility chart. The diagram is original and conceptual, not to scale and not a manufacturer installation drawing.

• LEDVANCE, “Light Bulb Sizes: A/B/C/CA/R/MR/BR/PAR/G/T Type Explained” — checked October 15, 2026; supports the general convention that the number indicates bulb diameter in eighths of an inch. The page’s 30/8 and 40/8 calculations apply that stated convention to BR30 and BR40.
• LEDVANCE, “BR30 vs. BR40: What’s the Difference?” — checked October 15, 2026; a plain-language BR30/BR40 reference used only alongside the naming and product-record sources below.
• LEDVANCE Contractor Series 5CCT Selectable LED Family, LED620R3 (January 2026) — source for both displayed SKUs: product fields on PDF p.2 (items 42575/42576), physical dimensions on p.3, and the damp-location line on p.1. No enclosed-fixture approval is inferred from the document’s separate A19 language.

Recheck the current lamp and fixture documentation for the exact model, configuration and installation conditions before purchase or replacement. To report a correction, use Contact.