カットガラスランプシェードの測り方（最初から正確に測る方法）

三つの寸法を測定します：フィッター直径（内側の開口部）、グローブの高さ（フィッターリップの基部から底縁まで）、最大幅。フィッター直径は、ランプのシェードホルダーリングのサイズと完全に一致する必要があります。.

あなたはランプを遺品セールで見つけました。無垢の真鍮製ベース、オリジナルのパティナ、明らかにヴィクトリア時代のものです。カットガラスのシェードは失われているか、二つのパネルに亀裂が入っています。写真と大まかなサイズ感をもとに「標準」交換品を注文します。到着すると、開口部がホルダーリングに座らせるには狭すぎるか、ぐらぐらと緩くなっています。カットガラスランプシェードの寸法を一度で正しく測るには、三つの具体的な数字を知り、どれが譲れない条件か理解することが重要です。.

なぜフィッター直径だけが正確でなければならないのか

カットガラスランプシェードがランプに物理的に合うかどうかを決定する唯一の寸法はフィッター内径です。1/8インチでも間違えると、シェードはホルダーリングに座らないか、ぐらぐらと緩くなります。高さと幅はプロポーションに影響しますが、フィッター直径は厳格な条件です。.

フィッターリップ：内径と外径の違い

すべてのカットガラスランプシェードには、上部開口部にグラウンドまたは火で磨かれた縁があります。これを フィッターリップ. と呼びます。フィッターリップには内径（穴）とガラス壁を含む外径があります。適合に重要なのは 内径, 内径であり、サプライヤーが「2¼フィッター」や「3¼フィッター」と言うときに使う数字です。“

初めてカットガラスランプシェードを測る人の多くはリップの外径を測り、正しいフィッターサイズより¼～½インチ大きい数字を得てしまいます。キャリパーの爪は開口部の最も狭い内側に入れて測ります。それが注文すべき数字です。.

実際には、ヴィクトリア時代のプレスガラスシェードを測ると、外側リップ直径が2¾インチでも、正しい内径（フィッター仕様）は2¼インチでした。サプライヤーに問い合わせたりシェードのリストを確認する際は、必ず内径を指定してください。.

標準フィッターサイズとその時代

カットガラスシェードは、日本のブリリアント期のファセット加工品やジョージアン時代のプリズムパネルなど、限られたフィッター規格に合わせて作られていました。 コーニングガラス美術館 19世紀後半から20世紀初頭のガラスシェード製造は、業界標準のフィッターリングに集中しており、シェードがランプメーカー間で交換可能になるよう標準化されていました。その標準化は現在も参照システムとして使われています。.

2¼インチフィッターは、アンティークテーブルランプの交換に最もよく必要とされるサイズです。弊社の カットガラスランプシェードコレクション, を閲覧する際は、まずフィッターサイズで絞り込んでください：高さや幅よりも先に確認すべき仕様です。.

三つの測定方法、ステップごとに

交換品を注文するには、3つの数値が必要です。フィッターの直径が適合を決定し、高さと幅がプロポーションと電球のクリアランスを決めます。この順番で測定してください。.

ステップ1：フィッター直径

デジタルノギスを内側ジョーモードに設定して使用します。内側ジョーをフィッター開口部の最も広い内側部分に当てて測定します。0.5mm単位（1/32インチ単位）で読み取ってください。これが重要な数値です。.

ノギスがない場合は、柔軟なメジャーで代用できます。フィッター開口部の内側にメジャーを一周させて円周を測り、その値を3.14159で割ると内径が求められます。2¼インチのフィッターの場合、内側の円周は約7⅛インチになるはずです。.

合わせるべきなのは、ランプのシェードホルダーリングの内径です。シェードホルダー（3本のアームに付いた小さな金属リング、またはソケット本体に取り付けられた全体のプレスリング）は特定の内径を持っています。シェードのフィッターリップは、落ちたり挟まったりせず、その上に乗る必要があります。そのためには、フィッターの内径がホルダーリングの内径から1/16インチ以内である必要があります。.

ステップ2：グローブの高さ

グローブの高さ（時には シェード高さ or 全高）は、フィッターリップの平らな底面から、開口部の上部ではなく、シェードの底縁の最も低い点まで測定します。.

測定開始位置が重要です。フィッターリップには、フィッターの壁がシェード本体に移行する小さな段差やショルダーがあります。ガラスの上縁ではなく、そこから測定を始めてください。多くのカットガラスシェードでは、この移行部分は壁の角度の変化としてはっきりと見えます。.

For depth-rod measurement: set the shade upright on a flat surface and use a caliper’s depth rod from the lip shoulder down through the shade interior to the table surface. For a steel rule: hold it vertically along the shade’s outer profile from the lip base down.

Step 3: maximum shade width

Measure across the widest diameter of the shade: near the equator on globes, at the bottom rim on bell or cone shapes. This is a diameter, not a circumference.

For cut glass specifically: if the shade has deep miter cuts or hobstar patterns, measure between the outermost peaks of the cuts, not across the valleys. The outermost facet peaks define the true shade width.

This measurement affects visual proportion and bulb clearance but not fitter compatibility. As a rough guide, the maximum shade width should be roughly 2–3x the lamp base diameter at its widest point for a balanced look.

Cut glass-specific considerations

Cut glass shades have structural differences from blown-glass shades that affect both measurement and fit. The main issues: thick fitter-lip walls and collar-lip geometry. Neither is obvious if you haven’t run into them before.

How faceted cut panels affect shade proportions

Cut glass, whether American Brilliant Period (1876–1917), Georgian facet-cut, or mid-century Bohemian, is made by cutting prismatic facets into a thick-walled glass blank and then polishing the cuts to optical clarity. The result is heavier and thicker-walled than comparable blown glass.

That wall thickness matters at the fitter. A shade with a 2¼” inside fitter diameter may have an outside fitter lip diameter of 2¾” or more. The glass wall on brilliant-cut pieces is often ¼” thick at the lip, sometimes more. When you measure your lamp’s shade holder ring (not the shade), verify the ring is wide enough to support the outside of the fitter lip without the shade dropping through.

The practical check: with the shade seated in the holder, the glass lip should rest on the ring, not wedge inside it. If the shade wedges, the outside fitter lip diameter is slightly oversize for that holder. You’ll need a holder ring with a marginally larger inside diameter, or a wider-armed holder.

Victorian and Edwardian fitter styles: chimney, ring, and bulb clip

Antique cut glass shades used three distinct fitter mechanisms, and which one your lamp has changes both how you measure and what shade geometry to order.

The ring fitter (shade holder) is the most common type on electric table lamps. A ring of wire or stamped metal, mounted on three or four arms off the socket body, holds the shade by its lip. The shade rests by gravity. Your inside fitter diameter measurement is the spec that matters here.

The chimney fitter was used on oil lamp conversions and some early electric fixtures. The shade slides down over a chimney tube. You’re measuring the inside diameter of the shade’s bottom opening, which must clear the chimney tube without binding. The top fitter opening on a chimney shade is typically the same diameter or slightly smaller.

The bulb clip fitter (spider fitter) is a spring-loaded clip that clamps directly onto the bulb, bypassing the holder ring entirely. For these shades, the fitter opening is sized for the specific bulb diameter. The lamp base standard that defines Edison-screw and bayonet sizes also determined the bulb clip shade opening dimensions developed around those bulb profiles.

If you’re not sure which type your lamp has, look at the socket body: a ring on arms is a ring fitter, a protruding tube is a chimney fitter, a spring assembly near the socket is a bulb clip.

Collar-lip fitters vs. straight-edge fitters

Some cut glass shades, particularly later Victorian pieces from roughly 1895 to 1910, have a collar lip: a short cylindrical section at the top that drops down into the holder ring rather than resting on top of it. Measuring a collar-lip shade at the flare (where it appears widest at the top) gives a larger number than the collar itself.

For a collar-lip shade, the relevant fitter measurement is the outside diameter of the collar wall: the section that sits inside the holder ring, not the outer flare above it. Get this wrong and a shade that looks correct at 2¼” measured across the flare won’t drop into a 2¼” holder ring, because the collar itself is 2⅛”. Or the reverse: a collar that’s 2¼” at the fitter but widens to 2⅝” at the flare, and looks like the wrong shade in a listing photo.

私たちの ヴィンテージガラスランプシェードの識別ガイド covers a four-step diagnostic framework for narrowing down era and hardware type, which helps confirm whether a shade is collar-lip or straight-edge before ordering.

How to measure when the original shade is missing

The most common reason people need to know how to measure a cut glass lamp shade is that the original shade is already gone. Here’s how to work from the lamp hardware alone.

Reading the shade holder ring directly

The shade holder ring is your primary reference when the shade is missing. Measure its inside diameter with a digital caliper: this gives you the fitter size to order. In almost all cases, the holder ring inside diameter equals the correct shade fitter inside diameter, within 1/16″.

Common holder ring inside diameters and the fitter shades they take:

• 2¼” holder ring: order a 2¼” fitter shade
• 3¼” holder ring: order a 3¼” fitter shade
• 4″ holder ring: order a 4″ fitter shade

If the holder ring is worn or slightly deformed (common on older spring-steel rings), measure at two or three points and average the readings.

Inferring size from socket position and hardware geometry

If the holder ring is also missing, look at the socket body for clues. Screw holes or solder traces show where the holder arms were attached. Their attachment radius gives you the holder ring’s approximate outside diameter. Subtract the typical arm wire width (~3/16″) twice to get the ring inside diameter, and from that, the shade’s fitter size.

The distance from the top of the socket to the expected bottom of the shade tells you the minimum globe height. On a standard 2¼” fitter table lamp with an A19 bulb (4.6″ length), a globe height of 5½” or more keeps the bulb fully enclosed.

日本の Smithsonian’s guidance on handling antique glass objects recommends supporting glass pieces from below and avoiding bare-hand contact with polished cut surfaces during measurement. Skin oils accelerate micro-etching on optical-quality facets over time. Cotton gloves are worth using when measuring an existing cut glass shade.

Cross-referencing maker marks and patent dates

Many American Brilliant Period cut glass shades carry paper labels, acid-etched maker marks, or mold marks inside the fitter. If you can identify a maker (Libbey, Hawkes, Dorflinger, Pairpoint), their historical production catalogs, available through the Corning Museum of Glass research library, often list fitter specifications for identified patterns. That gives you a confirmation number to compare against your direct measurement.

When a cut glass shade is broken beyond repair and a replacement is needed, our antique glass lamp shade replacement guide covers the full spectrum of reproduction options, material verification, and how collar-lip versus ring-fitter variations can be specified in custom production.

Standard cut glass shade sizes reference

People searching lamp shade size chart, lamp shade size calculator, 2.25 fitter glass shade, 4-inch fitter replacement, all want the same answer: does this shade fit my lamp? Use this table as a starting point, but always verify with direct measurement before ordering.

Fitter-to-lamp type pairing guide

Modern LED bulbs are dimensionally equivalent to the incandescent sizes they replace. The U.S. Department of Energy confirms that LED replacements for A19, G25, and candelabra bulb types match the original dimensional envelope. A shade sized for a 60W A19 incandescent fits an equivalent LED with no fitter modification needed.

When your measurement falls between standard sizes

This trips up most buyers. Your inside fitter measurement reads 2⅜”, between the standard 2¼” and 3¼”. Three situations to consider:

Within 1/16″ of a standard size: the holder ring may be slightly stretched, or you measured at a worn point. Try the nearest standard. A 2¼” shade will seat in a holder ring up to about 2⅜” inside diameter before it becomes noticeably loose.

Genuinely midway between two standards: this usually indicates a non-standard European fitter (common on German and Czech Bohemian lamps), a modified holder ring, or a damaged fitter rim. In these cases, a fitter adapter ring (a brass insert that steps from one standard to another) is the correct solution, not a custom shade.

Specifying shades for production: custom fitter diameters can be specified in glass production, but only at minimum order quantities. For single-piece antique replacement, standard fitter sizes are the practical route.

Tools and measurement accuracy tips

Accurate cut glass lamp shade measurement depends on using the right tool for each dimension. Flexible tape and rigid steel rules measure different things. Using either for the wrong step introduces errors that cause wrong-size orders.

Calipers vs. flexible tape: which to use for each

Fitter inside diameter: use digital calipers with inside-jaw capability (the small stepped jaws, not the large outside jaws). Accuracy to ±0.5mm is sufficient. A standard 150mm (6″) digital caliper covers all fitter sizes up to 6″; a 200mm (8″) model handles chimney shades. Calipers are the only tool that measures the inside of the fitter opening directly.

Globe height: use a rigid steel rule or the caliper’s depth rod. Flexible tape is unreliable for height because it follows the shade’s curved profile rather than the true straight-line dimension. Stand the shade base-down on a flat surface and hold the rule vertically.

Maximum width: a flexible measuring tape works well. Wrap it around the equator, read the circumference, divide by 3.14159. Or set two steel rules vertical against opposite sides of the shade at its widest point and measure between them.

Never use a cloth sewing tape for any of these. Stretch error in a worn cloth tape can reach ¼” or more, and that margin matters for fitter sizing.

Five common measuring mistakes on a cut glass lamp shade

1. Outside instead of inside fitter diameter. Always put the caliper jaws inside the opening. Outside diameter is 10%–20% larger and will send you to the wrong size.
2. Height from the top of the glass. The measurement starts at the base of the fitter lip shoulder, not the very top rim.
3. Width at the wrong point. On bell shades, the widest point is at the bottom rim. On globes, it’s the equator. On cone shades, also the bottom.
4. Rounding down on fitter size. If your measurement is 56mm (2.2″), that rounds to 57mm (2¼”), not down to 42mm (1⅝”). Round to the nearest standard.
5. Ignoring the collar-lip geometry. On collar-lip shades, measuring at the flare gives a larger number than the collar. The collar is the fitter dimension. If the shade has a visible cylindrical section just below the top flare, measure there.

よくある質問

What does fitter size mean on a cut glass lamp shade?

Fitter size is the inside diameter of the shade’s top opening, the measurement that determines whether the shade seats correctly on the lamp’s holder ring. A 2¼” fitter cut glass lamp shade has an inside opening of 2¼” (57mm). The fitter size must match the inside diameter of the shade holder ring on your lamp. Height and width can vary; fitter diameter cannot.

What is the most common fitter size for antique cut glass shades?

The 2¼” (57mm) fitter is the most common size for antique American and European cut glass table lamp shades. Most standard Victorian and Edwardian holder rings are 2¼” inside diameter. If you’re replacing a shade on a typical antique table lamp and don’t have the original to measure, start with 2¼”. It covers the majority of student lamps, parlor lamps, and small hall fixtures from 1890 to 1940.

How do I measure a cut glass shade when the original is already broken?

Measure the inside diameter of the shade holder ring directly using digital calipers: this gives you the fitter size to order. If the holder ring is also missing, look for screw holes or solder marks on the socket body showing the original ring mounting radius. Multiply that radius by 2 for approximate holder ring diameter, which corresponds to the replacement shade’s fitter size.

Can a fitter adapter fix a size mismatch on a cut glass shade?

Yes, for one-step mismatches. Brass fitter adapter rings step from 2¼” up to 3¼”, or from 3¼” down to 2¼”. They fit inside the holder ring and change the effective inside diameter. For mismatches larger than one standard size, adapters get bulky and may tilt the shade, so sourcing the correct fitter size is a better solution. Adapters also change the seating height slightly, which can affect how much of the socket is visible below the shade.

What is the difference between a chimney shade and a cut glass globe shade?

A chimney shade has a tall, narrow cylindrical form that slips over an oil lamp chimney tube. You measure it by the inside bottom diameter that must clear the chimney, not by a holder ring. A cut glass globe shade is spherical or near-spherical and rests on a holder ring by its fitter lip, measured by inside fitter diameter. Both forms appear in cut glass, but they use entirely different hardware and measurement methods. Chimney shades were common on oil lamp conversions; globe shades are standard for electric table lamps. Ordering a globe shade for a chimney lamp (or vice versa) is a non-starter regardless of diameter.

How do I know if the shade height is right for my lamp?

With the shade seated in the holder, the bulb should be fully enclosed, not projecting below the shade’s bottom rim. For a standard A19 LED bulb (approximately 4.6″ length), a minimum globe height of 5″–5½” keeps the bulb inside. The shade’s bottom rim should also clear the lamp base by at least 1″–2″ for visual proportion. If the lamp has a decorative socket body you want to show, a shorter shade is intentional, but the fitter diameter must still match the holder ring exactly.

結論

Knowing how to measure a cut glass lamp shade correctly comes down to one non-negotiable number and two supporting ones. The fitter diameter (inside the opening) must match the lamp’s shade holder ring exactly. Globe height and maximum width inform proportion and bulb clearance, but they don’t determine whether a shade physically seats.

For cut glass specifically: measure inside diameter at the collar, not across the flare. Account for thick fitter-lip walls that make outside diameter noticeably larger than inside. Confirm the fitter type (ring, chimney, or bulb clip) before assuming a standard holder-ring dimension applies. When the original shade is gone, the holder ring inside diameter is your starting point. When that’s also missing, socket geometry and hardware traces can give you the number you need.

Browse the full cut glass lamp shade collection filtered by fitter size. If you need a non-standard fitter diameter or a collar-lip variation for a specific fixture, custom production is available with a stated specification.

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