Ordering a replacement oil seal should be simple — but one wrong millimeter and you are staring at a seal that either spins loose in the bore or burns up on the shaft. The good news: virtually every metric oil seal in the world follows the same three-number size system, and once you understand it, finding your part takes minutes.
This guide gives you a complete metric oil seal size chart covering the most common shaft diameters from 10 mm to 100 mm and beyond, explains exactly how to read and measure seal dimensions, and includes a millimeter-to-inch conversion table for equipment built with imperial parts.
Whether you are rebuilding an electric motor, servicing a gearbox, or fixing a leaking pump, use the charts below to pin down your size — then search it directly in our oil seal shop, which stocks more than 20,000 metric sizes with a minimum order of just one piece.
How Oil Seal Sizes Are Written
Every metric oil seal is described by three dimensions, always in this order and always in millimeters:
Shaft diameter (ID) × Outer diameter (OD) × Width (W)
For example, TC 25x47x7 means:
- 25 mm — inner diameter, matching the shaft the seal rides on
- 47 mm — outer diameter, matching the housing bore the seal presses into
- 7 mm — width (thickness) of the seal in its groove
The letters in front of the numbers describe the seal type:
- TC — double-lip rotary shaft seal with a garter spring, by far the most common type (see our TC oil seals)
- TB / TG / TA — variations with fewer lips or a springless design
- X (four-lip star seal) — an alternative rotary design with extra sealing margins (view X-type seals)
- Split seals — two-piece seals installed without disassembling the shaft (view split oil seals)
Two details worth remembering when you compare sizes:
- The ID follows the shaft, not the old seal. A worn seal often measures 0.5–2 mm larger than the shaft because the lip has worn away. Always measure the shaft itself when in doubt.
- Tolerances matter. Metric seals follow the dimensional system of DIN 3760, so a 25x47x7 seal from any manufacturer fits the same 25 mm shaft and 47 mm bore. That is why cross-referencing between brands works so cleanly.
How to Measure Your Oil Seal in 3 Steps
Before you use the size chart below, confirm your three measurements with a digital caliper. For a full walkthrough with photos, see our how to measure an oil seal guide — the short version:
Step 1: Measure the shaft diameter (ID)
Clean the shaft where the seal runs, then measure its outside diameter with the caliper jaws at 90° positions. Take two readings and use the smaller one if they differ — that is the true shaft size you must match.
Step 2: Measure the housing bore (OD)
If the old seal is still installed, measure its outer edge. If it is already out, measure the bore inside the housing. Round to the nearest whole millimeter; metric bores are almost always integer values (40, 45, 47, 52, 62 mm, and so on).
Step 3: Measure the width
Place the seal flat and measure from face to face. Most standard metric seals are 7, 8, 10, or 12 mm wide. If your groove is slightly deeper than the seal, a narrower seal usually still works — a seal wider than the groove will not.
Tip: If the old seal is badly worn or the part number is unreadable, measuring the shaft and bore directly is more reliable than measuring the seal itself. Once you have your three numbers, head to our measurement guide for tolerance and rounding rules.
Metric Oil Seal Size Chart: Most Common Sizes
The tables below list the most frequently ordered metric oil seal sizes (ID × OD × Width, all in mm), grouped by shaft range. Sizes in bold are among the highest-volume sellers worldwide.
Small shafts: 10–20 mm ID
| Size (ID × OD × W) | Typical application |
|---|---|
| 10x25x7 | Small electric motors, power tools |
| 12x28x7 | Small pumps, fan motors |
| 15x30x7 | Fan motors, small water pumps |
| 15x35x7 | Light-duty gearboxes |
| 17x35x7 | Light machinery, small engines |
| 20x35x7 | Motorcycles, hydraulic pumps |
| 20x40x7 | Motorcycle engines, small motors |
| 20x42x7 | Agricultural pump shafts |
Mid-range shafts: 25–40 mm ID
| Size (ID × OD × W) | Typical application |
|---|---|
| 25x40x7 | Electric motors |
| 25x47x7 | Electric motors, gear reducers — one of the most common sizes in existence |
| 30x47x7 | Motors, gearbox output shafts |
| 30x52x7 | Centrifugal pumps |
| 32x52x10 | Industrial motors |
| 32x58x10 | Worm gear reducers |
| 35x52x7 | Pumps, motors |
| 35x58x10 | Gear reducers, mixers |
| 40x62x10 | Gearbox input/output shafts |
Industrial & agricultural shafts: 45–70 mm ID
| Size (ID × OD × W) | Typical application |
|---|---|
| 45x65x8 | Hydraulic pumps |
| 45x65x10 | Agricultural machinery, PTO shafts |
| 50x72x10 | Industrial motors, conveyors |
| 50x80x10 | Tractors and farm equipment |
| 55x80x10 | Heavy equipment, crushers |
| 60x85x10 | Large gearbox output shafts |
| 60x90x10 | Agricultural machinery |
| 65x90x12 | Heavy-duty axles |
| 70x95x12 | Construction machinery |
Large shafts: 75–100+ mm ID
| Size (ID × OD × W) | Typical application |
|---|---|
| 75x100x12 | Large gear reducers |
| 80x105x12 | Heavy-duty gearboxes |
| 80x110x12 | Milling and mining equipment |
| 85x110x12 | Large shafts — often serviced with split seals |
| 90x120x12 | Large industrial shafts |
| 100x125x12 | Large shafts, paper and steel mills |
| 100x130x12 | Heavy industrial applications |
Don’t see your size? This chart covers best-sellers only. We stock 20,000+ metric sizes from a few millimeters up to 200 mm and beyond — search any combination in our shop or ask us directly.
Common Oil Seal Sizes by Application
If you know your equipment type but not the exact size, these patterns hold for most machinery:
- Electric motors — usually small to mid-range TC seals, 7 mm wide: 15x30x7 through 35x58x7. Check our TC oil seals category for these sizes.
- Gearboxes and reducers — mid-range sizes, often 10 mm wide: 30x52x7, 35x58x10, 40x62x10, 50x72x10.
- Centrifugal pumps — commonly 30x52x7, 35x58x10, 40x62x10; wet or chemical duties usually call for FKM (Viton) rather than standard NBR — compare options in the material guide.
- Agricultural machinery — larger sizes such as 45x65x10, 50x80x10, 60x90x10; farm seals take dirt and shock loads, so double-lip TC with a spring is the default choice.
- Trucks and heavy equipment — 55 mm ID and up, often 12 mm wide: 65x90x12, 70x95x12, 80x110x12.
- Large slow-turning shafts — 85 mm ID and above, where a split oil seal can save you from pulling the entire shaft apart.
Millimeter to Inch Conversion Table
Many machines built in the US or UK use inch-size seals, but the two systems overlap more than you’d expect — and any metric measurement can be converted for cross-referencing.
| mm | inch | mm | inch |
|---|---|---|---|
| 10 | 0.394 | 55 | 2.165 |
| 12 | 0.472 | 60 | 2.362 |
| 15 | 0.591 | 65 | 2.559 |
| 17 | 0.669 | 70 | 2.756 |
| 20 | 0.787 | 75 | 2.953 |
| 25 | 0.984 | 80 | 3.150 |
| 30 | 1.181 | 85 | 3.346 |
| 35 | 1.378 | 90 | 3.543 |
| 40 | 1.575 | 95 | 3.740 |
| 45 | 1.772 | 100 | 3.937 |
| 50 | 1.969 | 110 | 4.331 |
Quick rules of thumb:
- If your caliper reading lands on a round decimal like 0.984″ or 1.969″, your equipment almost certainly takes a metric seal (25 mm, 50 mm).
- If the ID measures exactly 1.000″, 1.250″, 1.500″ and so on, you have an imperial-series seal — match it by cross-referencing the part number instead.
- Have an old part number from SKF, NOK, NAK, Corteco, or another brand? Use our oil seal cross reference tool to convert it into our equivalent part number in seconds.
How to Find Your Seal Fast: The 3-Step Route
Use whichever entry point matches what you are holding right now:
- You have a part number (SKF, NOK, NAK, Corteco, Freudenberg, etc.) → plug it into our cross reference tool to get the equivalent size and our part number.
- You have measurements → take your ID × OD × Width and search it in the shop. Every product is listed by metric dimensions (e.g., “TC 25x47x7 NBR”), so you can match it exactly. We stock 20,000+ sizes and accept orders of a single piece — no minimum quantity.
- You have neither → send us a photo of the old seal plus any measurements you were able to take via the contact page or WhatsApp, and we will identify it for you before you order.
Once you order, seals ship within 72 hours at one flat shipping rate worldwide, regardless of weight or destination. Not sure about material? NBR is the standard choice for oil and grease duties; for high temperatures or aggressive media, check our material guide before checkout.
Frequently Asked Questions
1. How do I know what size oil seal I need?
Measure three dimensions with a caliper: the shaft diameter (inner diameter), the housing bore (outer diameter), and the seal width. Write them in that order — for example, 25x47x7 — and look them up in a size chart or search them directly in a shop that sells by metric dimensions. For step-by-step instructions, see our measurement guide.
2. What do the three numbers on an oil seal mean?
They are ID × OD × Width in millimeters. The first number is the shaft diameter the seal runs on, the second is the bore it presses into, and the third is its thickness. A TC 30x52x7 seal fits a 30 mm shaft in a 52 mm bore and is 7 mm wide.
3. What does “TC” mean in an oil seal listing?
TC designates a double-lip rotary shaft seal with a garter spring — the workhorse seal for keeping oil in and dirt out on rotating shafts. It covers the vast majority of motor, gearbox, pump, and agricultural applications. Browse TC seals in all stocked sizes here.
4. Are oil seal sizes metric or inch?
Both exist, but metric (ID × OD × W in millimeters, per the DIN 3760 system) is the worldwide standard. Imperial seals use fractional inches and are common on older US/UK equipment. If your measurements convert to round decimals (e.g., 25 mm ≈ 0.984″), you have a metric seal; if they land exactly on fractions like 1.250″, cross-reference the part number instead.
5. Can I order just one oil seal, and how fast does it ship?
Yes. We sell with a minimum order of one piece and ship within 72 hours of your order, at a single flat shipping rate to any country. Double-check your measurements before ordering — we cannot accept returns for seals ordered in the wrong size — but our team is happy to confirm your dimensions first via the help center or contact page.
Ready to Find Your Seal?
Search your size (ID × OD × Width) in our oil seal shop — 20,000+ metric sizes in stock, order from one piece, ships within 72 hours worldwide. Can’t find it in the chart? Send us your measurements or old part number and we’ll source it: Request a quote.