Mower Belt and Blade Cross-Reference
This page does not list OEM part numbers, on purpose. Published cross-reference lists go stale the moment a manufacturer revises a deck, and a wrong part number costs more than a lookup. What this page gives you instead is everything you need to identify the belt or blade you are actually holding and to specify a replacement correctly.
1. Where the identification plate lives
| Machine | Plate location | What to record |
|---|---|---|
| Walk-behind mower | Rear of the deck, or under the handle bracket | Model number and type/serial code |
| Lawn tractor | Frame rail under the seat pan | Model, serial, deck part number |
| Zero-turn | Frame beside the engine or under the seat deck | Model, serial, deck size code |
| Separate mower deck | Sticker on the deck shell near the discharge chute | Deck model number (outranks the tractor model) |
| Engine (tune-up parts) | Blower housing or valve cover | Engine model, type and code |
Photograph the plate. Many parts lists split one model into "before serial" and "after serial" ranges.
2. V-belt section dimensions
| Section | Top width | Depth | Length specified as | Where used |
|---|---|---|---|---|
| 3L | 3/8" | 7/32" | Outside circumference | Light accessory drives |
| 4L (FHP) | 1/2" | 5/16" | Outside circumference | Most homeowner deck and drive belts |
| A (classical) | 1/2" | 11/32" | Inside / effective length | Industrial equivalent of 4L |
| 5L | 21/32" | 3/8" | Outside circumference | Larger decks, heavier drives |
| B (classical) | 21/32" | 13/32" | Inside / effective length | Industrial equivalent of 5L |
| AA (double-V) | 1/2" | Symmetrical | Outside circumference | Decks with a back-side idler |
| BB (double-V) | 21/32" | Symmetrical | Outside circumference | Larger decks with a back-side idler |
A designation like 4L920 means a 4L section, 92.0 inches outside. A90 means an
A section with a 90 inch inside length, which is roughly 92 inches outside. Same belt family, two
conventions.
3. Blade centre-hole patterns
| Pattern | Description | Note |
|---|---|---|
| Round hole | Single round bore, commonly 5/8" or 3/4" | Measure the bore; bushings are sometimes fitted |
| 5-point star | Five-lobed centre | Common on many walk-behind and tractor decks |
| 6-point star | Six-lobed centre | Not interchangeable with 5-point |
| 7-point star | Seven-lobed centre | Check lobe count, not just the look |
| H-pattern / bowtie | Rectangular slot with tabs | Orientation matters on refit |
| Round with outer holes | Round bore plus two locating holes | Record the hole centre spacing |
Blade specification also needs overall length (tip to tip) and, for high-lift and mulching blades, the lift height. Record all three: length, centre pattern, lift style.
4. Measuring effective belt length — the string method
- Remove the old belt and note the exact path, including which side of each idler it runs on. Photograph it.
- Run non-stretch cord (mason line works) around the same path.
- Move the tensioner to its normal running position and hold it there.
- Mark the cord where it overlaps, release, lay it flat and measure.
- Cross-check against a parts list. If the two disagree by more than about 1%, re-check the routing.
5. Diagnose before you replace
| Symptom | Likely cause | Check |
|---|---|---|
| Squeal on PTO engagement | Glazed belt or weak tensioner | Belt sides shiny; spring stretched or unhooked |
| Blades slow under load | Belt slip or seized spindle | Spin each spindle by hand |
| Burning smell | Belt rubbing a keeper or frozen idler | Look for a shiny wear line on the deck shell |
| Belt thrown repeatedly | Bent belt keeper or bent deck bracket | Straight edge across the keepers |
| Vibration | Unbalanced or bent blade | Balance the blade on a nail after sharpening |
| Cracks in the belt back | Age or a tight reverse bend | Replace, and check the back-side idler |
6. Method note
The belt section and blade centre-pattern dimensions on this page are published industry standards and do not vary by brand. Everything model-specific — belt lengths, blade lengths, OEM numbers — is deliberately left to your machine plate, because that is the only source that stays correct across production changes. If you find a cross-reference list that contradicts your plate, believe the plate.
7. Frequently asked
Can I order a mower belt by deck width alone?
No. Belt length is set by the pulley and idler layout, not by cutting width, and manufacturers change that layout between model years while keeping the deck width the same. Order from the model and serial number on the deck or frame plate.
How do I measure a mower belt that has already stretched?
Do not measure the failed belt directly, because a worn belt typically reads one to two percent long. Instead run non-stretch cord around every pulley in the exact belt path with the tensioner in its running position, mark the cord and measure it flat.
What is the difference between a 4L belt and an A belt?
Both are 1/2 inch across the top, but a 4L belt is 5/16 inch deep and is specified by outside circumference, while an A section belt is 11/32 inch deep and is specified by inside or effective length. Mixing the two conventions puts you about two inches out.
What is a double-V or hex belt?
A belt with V-shaped faces on both sides, used on decks where the belt wraps a back-side idler pulley. A single-V belt will slip on that idler, so a double-V belt cannot be substituted with a standard one.
Why did my new mower belt fail quickly?
The usual causes are a seized or noisy idler bearing, a weak or unhooked tensioner spring, a bent belt keeper, or a belt one size short being run over-tight. Spin every pulley by hand before fitting a replacement.
Shop the parts
Belts and pulleys · Blades · Wheels, tires and bearings · Tune-up parts. By machine: Cub Cadet · John Deere · Troy-Bilt · MTD · Husqvarna · Toro · Craftsman · Briggs & Stratton. Free US shipping.
Related reading: mower deck belt sizing guide.
Aftermarket and OEM-compatible parts. PatioZora is not affiliated with or endorsed by the brands named on this page; brand names are used to indicate fitment only. Figures on this page are published reference standards and general guidance — always confirm against the stamp, plate or manual on your own equipment.