Fareed Mohmed · Engineering

Timing Belt Drive Selector

Pulleys · Centre distance · Max torque

Choose the pulley tooth counts, centre distance, speed and the torque you need to carry. The tool works out the belt length and teeth in mesh, suggests a steel-cord polyurethane belt profile and width, and shows the maximum torque each standard width can transmit.

Ratings are the tooth-force and tensile-load values published by Ammeraal Beltech for its PU Torque Steel belts (T5, AT5, T10, AT10, AT20, HTD5M, HTD8M, HTD14M). Other makes rate belts differently, so treat the result as a first selection and confirm it against your supplier's catalogue before ordering.

Start Here: The Selection Process

Eleven steps from the application to the part number, in the order the tool works. Read this once, then use sections 01, 02 and 03. Steps with a button link to the place where you enter or read that step. Steps 9 and 10 are done outside the tool.

Define the application

Write down what the drive must do before you pick any belt.

Power in kW and the driver speed in RPM, or the torque on the driver shaft directly
Power transmission, or linear positioning (this needs a low-stretch steel-cord belt and a backlash check)
Duty: continuous, intermittent, or reversing; shock and jam risk
Space, environment (heat, oil, dust, food contact) and the life you need

What the tool asks: speed, the required torque on the driver shaft, and a service factor. If you only know power, torque = 9549 × kW / RPM. Duty, environment and life have no input: use them for the service factor and for step 10.

Enter it in section 01 →

Apply the service factor

Machines start, stall and shock, so the belt is sized for a larger torque than the average: design torque = torque × service factor. The same idea works with power.

In this tool: pick from 1.0 (smooth, no shock) to 2.0 (severe shock, jam risk). Catalogue procedures such as Gates add about 0.2 for an idler, add 0.1 to 0.4 for speed-up drives, and subtract 0.2 for intermittent duty. The tool does not add these for you, so choose the next higher factor for a speed-up drive or an idler. Load reversal and heavy shock need the supplier’s advice.

Set it in section 01 →

Choose the belt profile (pitch)

The profile sets the tooth pitch and the strength per millimetre of width. A bigger pitch carries more torque. At the same width the AT profiles carry more than the T profiles: for 10 mm wide belts the tensile rating is 560 N for AT5 against 390 N for T5.

T5, T10: trapezoidal teeth, simple and common
AT5, AT10, AT20: stronger, for higher loads
HTD 5M, 8M, 14M: curved teeth, smoother, from light to heavy drives

Fresher tip: you do not have to guess. Leave the profile on Best match, and the tool compares every profile for your drive.

Compare profiles in section 07 →

Choose the pulleys

The small pulley sets the belt speed and how sharply the belt bends. Too few teeth shortens belt life and reduces the rating.

Smallest teeth the tool accepts: T5 10, T10 12, AT5 and AT10 15, HTD 5M 16, HTD 8M 18, AT20 18, HTD 14M 28
Speed ratio = driven teeth ÷ driver teeth
Belt speed = π × pitch diameter × RPM / 60000 (m/s). The tool warns above 40 m/s

Why the minimum differs: the limits come from the catalogue data, and the larger pitches need more teeth. A single rule such as “at least 14 to 20 teeth” is not safe for HTD 14M.

Pick the teeth in section 01 →

Set the centre distance and belt length

The tool computes the belt length from the pulleys and the centre distance, rounds it to a whole number of belt teeth, then recalculates the centre distance for that belt.

Steel-cord PU belts are normally made endless to any tooth count; stock sizes can be chosen instead
Make one shaft adjustable. The tool shows the take-up needed
For linear motion use an open-ended belt, not a closed one

See length and fit in section 05 →

Check wrap and teeth in mesh

Only the teeth that are engaged on the small pulley carry the load. More wrap means more teeth in mesh and a higher rating, up to 12 teeth.

Aim for at least 6 teeth in mesh. The tool warns below that
Wrap on the small pulley should be 120° or more. The tool warns below that
If either is low: more centre distance, a smaller ratio, or an idler

Read the warnings in section 03 →

Select the belt width, last

Width comes after the pulleys, centre distance and belt length, because the teeth in mesh decide how much each millimetre of width can carry. The tool picks the narrowest standard width whose maximum torque is at least the design torque.

Why not earlier: choosing a width before the pulleys are fixed means redoing it every time the pulleys change. Catalogue design procedures put the width last for the same reason.

See the width in section 03 →

Check strength

The tool takes the smaller of two limits: tooth shear (the teeth stripping) and the allowable tensile load of the cord. Each catalogue gives its own values, and the results are shown for each one. Section 02 checks your drive against every belt from every brand and lists the ones that pass, with the reason each of the others fails.

Not checked by the tool: belt pre-tension, shaft and bearing loads, belt stretch and backlash for positioning, and noise. For a positioning axis use the supplier’s accuracy data.

See which brands and belts pass in section 02 → See each catalogue in section 04 →

Choose the pulleys in detail

Pulley type, material (aluminium or steel), bore, keyway or taper lock, and flanges are chosen with the pulley supplier. The tool lists pulley codes only for MISUMI, and warns when the centre distance is too small for the pulleys and their flanges.

Check the environment

Check temperature range, oil and chemicals, moisture, food contact and static (ESD) with the belt supplier. The ratings in the tool are for steel-cord polyurethane belts; rubber belts carry less. These checks are not in the tool.

Finalise and order

Take the profile, width, tooth count and length from the result
Use the brand part numbers as a starting point and confirm the exact order code with the supplier
Check stock, cost and delivery

See part numbers in section 06 →

Six common mistakes

Picking the width firstThe width depends on teeth in mesh, which depends on the pulleys and centre distance. Choose it last.

Pulleys below the minimum teethShort belt life and a lower rating. The minimum rises with the pitch.

Skipping the service factorSizing on average torque and failing at start-up or shock.

Ignoring wrap and teeth in meshWith fewer than 6 teeth in mesh the belt can jump teeth.

Using a rubber-belt rating for a steel PU beltOr the reverse. The ratings in this tool are for steel-cord polyurethane belts unless the table says otherwise.

Trusting an unrated beltSKF, Brecoflex, Optibelt and MISUMI rubber belts are listed with part numbers but are not strength-checked here.

Brands that make this product

Filled gold: loaded in this tool and rated from the catalogue. Outlined gold: loaded for part numbers only, not strength-checked. Grey dashed: not loaded yet. Hover a brand for what is loaded.

Ammeraal Beltechrated

Gatesrated

Cross & Morserated

ContiTechrated

MISUMIrated

Brecoflexpart numbers

Optibeltpart numbers

SKFpart numbers

Megadynenot yet

Mitsuboshinot yet

Bandonot yet

Tsubakinot yet

SITnot yet

Fennernot yet

Elatechnot yet

To use a brand that is not loaded, take the design torque and the pulley and belt data from section 03 to that brand’s catalogue and follow the same steps: profile first, width last. The “Your belt” list in section 01 offers only the loaded brands.

See every hardware and brand →

Brand names and logos are trademarks of their owners and are shown only to identify catalogues.

Drive Details

Every input is a dropdown. Pulley A is the driver. The required torque is the torque on the driver shaft.

Driver pulley Anumber of teeth

Driven pulley Bnumber of teeth

Centre distancemm, shaft to shaft

Driver speedRPM

Required torque (driver shaft)N·m

Service factordesign torque = torque × factor

Profile for the width tableBest match picks the narrowest belt that passes

Belt supplymade to length, or common stock sizes

Calculation methodapplies to the catalogue picks and your belt; see Calculation Steps

Your belt optional

Optional. Skip this to get the suggested belts below. Or pick a brand, model and width to see how that belt performs in this drive. The result appears at the top of the Result section.

Brand (catalogue)strength data comes from that catalogue

Belt modelprofile and pitch

Belt widthmm, standard widths with published ratings

Belt lengthbest fit, or a stock length near yours

Brands And Belts That Pass

Your drive is checked against every belt in every catalogue loaded: each brand, each profile and each standard width. A belt is listed when at least one standard width carries your design torque, with enough teeth on both pulleys and a belt long enough for the catalogue. It uses the same calculation method you chose in section 01. Each card shows how many belts in that catalogue pass. Click a card to see only that brand. Press Select on a row to load that belt into Your belt and see the full working in section 03.

Result

Belt From Each Catalogue

Show every profile for every catalogue

Standard Belt Size & Fit

Keep the centre distance: pulley pairs that fit a standard belt

Same speed ratio as your drive, so the driven speed does not change. Pulley diameters change, so re-check the torque result above for the pair you pick.

Brand Part Numbers

Designations follow each brand's usual pattern, with width and length in mm. Endless belts are made to your length. Confirm lengths and widths in stock with the supplier.

Allowable tensile load for a 25 mm belt, by brand

Values in N for a 25 mm wide belt. Ammeraal and Gates are both steel-cord, open-ended ratings (Gates states 12 or more teeth in mesh), so those two are close to a like-for-like comparison. Cross & Morse gives a maximum belt tension, not an open-end or welded rating. The Optibelt belt has an aramid cord and is not comparable. For other widths, scale roughly in proportion to width.

Suggested Belt by Profile

For your pulley tooth counts, each profile gives different pulley diameters, so wrap and teeth in mesh change. The narrowest standard width that carries the design torque is shown for each one.

The highlighted row is the narrowest passing belt, using the smaller pitch when widths tie. A dash means no standard width carries the load, or a pulley is below the profile's minimum teeth.

Maximum Torque by Belt Width

Maximum torque is on the driver shaft. Each belt carries the smaller of its tooth-force limit and its allowable tensile load.

Calculation Steps

How each catalogue is calculated

SKF Timing Belt Range

The SKF Power Transmission Products catalogue lists belts in the PHG range: classical, HTD, super torque and metric polyurethane profiles. It gives the tooth form and the lengths made, but no tooth-force, tensile or power-rating table. So the tool does not strength-check SKF belts. For the profiles it does rate (T5, AT5, T10, AT10, AT20, HTD 5M, 8M, 14M) it shows the SKF order designation and nearest listed length in the brand table above, and the strength used is the Ammeraal value. The other profiles are listed here for reference and for sourcing.

Family	Profile	Pitch (mm)	Belt thickness (mm)	Tooth height (mm)	Tooth angle	Lengths listed	Pitch length range (mm)	Construction
Classical	MXL	2.032	1.14	0.51	40°	161	53 – 4,154	Neoprene, glass cord, nylon facing
Classical	XL	5.08	2.30	1.27	50°	145	112 – 5,405	Neoprene, glass cord, nylon facing
Classical	L	9.525	3.60	1.91	40°	114	170 – 5,075	Neoprene, glass cord, nylon facing
Classical	H	12.7	4.30	2.29	40°	148	368 – 6,909	Neoprene, glass cord, nylon facing
Classical	XH	22.225	11.20	6.35	40°	29	1,176 – 5,778	Neoprene, glass cord, nylon facing
Classical	XXH	31.75	15.70	9.53	40°	17	1,588 – 5,080	Neoprene, glass cord, nylon facing
HTD	3M	3	2.4	1.20	—	162	60 – 6,804	Neoprene, glass cord, nylon facing
HTD	5M	5	3.6	2.10	—	178	180 – 7,000	Neoprene, glass cord, nylon facing
HTD	8M	8	5.6	3.88	—	165	184 – 6,880	Neoprene, glass cord, nylon facing
HTD	14M	14	10.0	6.10	—	49	938 – 3,668	Neoprene, glass cord, nylon facing
Super torque (STS)	S2M	2	1.36	0.76	—	44	60 – 3,700	Neoprene, high-strength cord
Super torque (STS)	S3M	3	2.20	1.14	—	94	120 – 6,510	Neoprene, high-strength cord
Super torque (STS)	S4.5M	4.5	—	—	—	32	180 – 932	Neoprene, high-strength cord
Super torque (STS)	S5M	5	3.41	1.91	—	57	150 – 4,000	Neoprene, high-strength cord
Super torque (STS)	S8M	8	5.30	3.05	—	126	376 – 6,640	Neoprene, high-strength cord
Super torque (STS)	S14M	14	10.20	5.30	—	33	714 – 5,012	Neoprene, high-strength cord
Metric PU	T2.5	2.5	1.3	0.7	40°	42	102 – 1,345	Polyurethane, steel or aramid cord
Metric PU	T5	5	2.2	1.2	40°	117	115 – 4,075	Polyurethane, steel or aramid cord
Metric PU	T10	10	4.5	2.5	40°	124	260 – 7,050	Polyurethane, steel or aramid cord
Metric PU	T20	20	8.0	5.0	40°	23	880 – 5,000	Polyurethane, steel or aramid cord
Metric PU	AT5	5	2.7	1.2	50°	17	220 – 1,520	Polyurethane, steel or aramid cord
Metric PU	AT10	10	5.0	2.5	50°	28	500 – 4,030	Polyurethane, steel or aramid cord
Metric PU	AT20	20	8.0	5.0	50°	5	1,000 – 2,360	Polyurethane, steel or aramid cord

Classical lengths are converted from the inch designation, so they are approximate. Double-sided belts are also made: Double-sided classical (D-XL, D-L, D-H), 283 lengths; Double-sided HTD (DA-5M, 8M, 14M), 286 lengths; Double-sided super torque (DS5M, DS8M), 153 lengths; Double-sided metric (DB-T5, DB-T10), 119 lengths. Order designation: PHG, then length, profile and width (HTD, classical and super torque); PHG, profile, length and width (metric PU). Non-standard lengths and open-ended rolls are available on request from SKF. Source: SKF Power Transmission Products catalogue 11015, belts section.

How It Is Calculated

Geometry

Pitch diameter d = z × pitch / π. Belt pitch length L = 2C + π(D + d)/2 + (D − d)²/(4C), rounded to a whole number of belt teeth. The actual centre distance is then recalculated for that tooth count, and the two neighbouring tooth counts are shown so you can pick a length your supplier stocks.

Standard belt size

Steel-cord PU belts are normally welded endless from rolled belting, so any whole number of teeth is a standard length. The tool rounds the calculated length to the nearest tooth count, then recalculates the centre distance needed for that belt. In the stock-size mode it chooses from stocked lengths for the profile: the Gates Synchro-Power catalogue lists for T5, AT5, T10 and AT10, and common distributor sizes for HTD8M and HTD14M. AT20 is shown as made to length. Confirm availability with your supplier.

Teeth in mesh

Wrap on the smaller pulley is 180° − 2·asin((D − d)/2C), and teeth in mesh is z_small × wrap / 360 rounded down. The rating counts at most 12 teeth in mesh, so more wrap beyond that adds no capacity. Fewer than 6 teeth in mesh is flagged.

Torque capacity

The manufacturer's specific tooth force (N per mm of belt width, per tooth in mesh) falls with speed, and is read at the smaller pulley's RPM with linear interpolation. Tooth-limited pull = specific tooth force × width × teeth in mesh. This is compared with the allowable tensile load for the width (the "open end & torque" column), and the smaller one governs. Maximum torque = governing pull × driver pitch radius.

Pass / fail

A belt passes when its maximum torque is at least the required torque × the service factor. Belt pre-tension, shaft loads, belt speed limits and pulley flange design are outside this tool. The ratings are for steel-cord polyurethane belts, so rubber (neoprene) belts will carry less.

Belt from each catalogue

Each catalogue is rated on its own published data. Ammeraal Beltech has tooth-force and tensile tables for eight profiles. Cross & Morse publishes tooth shear strength by speed and maximum belt tension by width for T5, AT5, T10 and AT10, so its widths are the ones with a published tension. Gates publishes, for each width, an allowable belt force (open-ended and endless welded) and an allowable effective force at 12 or more teeth in mesh, for T5, AT5, T10, AT10, AT20, HTD5M, HTD8M, HTD14M and the stronger-cord HTDL14M. The tool scales the Gates effective force down in proportion when fewer than 12 teeth are in mesh, and uses the welded rating for endless belts. Gates stock sizes decide the part numbers. Cross & Morse rubber RPP belts and Gates rubber belts are not covered. ContiTech SYNCHROBELT HTD rubber belts (glass cord) are rated from ContiTech power rating tables, the teeth-in-mesh factor and length factor from its design data, and the permissible effective pull per width. This tool treats your service factor as ContiTech's overall service factor. The ContiTech open-ended polyurethane belts are not rated. The Brecoflex and Optibelt designations are built from their order patterns and are not strength-checked either.

MISUMI Economy series

Two MISUMI catalogues are added: open-end and closed-end polyurethane belts with steel cord, in T5, T10, HTD 5M and HTD 8M. MISUMI prints an allowable tension for each width, and the tool uses it as the effective force the belt can carry; the catalogue gives no teeth-in-mesh factor, so none is applied. Closed-end (bonded) belts carry much less than open-end belts. The belt must have at least the minimum number of teeth the catalogue lists (T5 60 open, 96 closed; T10 40 and 52; HTD 5M 60 and 104; HTD 8M 40 and 65). MISUMI rubber belts (S2M to S8M, HTD 3M to 8M, MXL, XL, L, H, T5, T10) and pulleys are listed in the order-code table with stock lengths and pulley sizes, but MISUMI gives no power rating for them and refers to a national (GB) design manual, so they are not strength-checked. Pulley minimum teeth for the two PU belts are the smallest MISUMI offers: T5 12, T10 12, S5M 14, S8M 18. The third entry, MISUMI urethane belt, follows the rule in MISUMI technical data B-036: for belts used other than for conveying, design with about 2/3 of the open-end urethane allowable tension in MISUMI’s reference table (T5 25 mm: 497 N, so 331 N; 1/2 for S3M and H3M, which this tool does not list). Its minimum pulley teeth are MISUMI’s Table 6 values (T5 12, T10 14, HTD 5M 14, HTD 8M 24).

Source

SKF Power Transmission Products catalogue 11015, belts section (tooth forms and stock lengths only, no ratings). Ammeraal Beltech PU Torque Steel datasheets (T5, AT5, T10, AT10 NT, AT20, HTD5M, HTD8M, HTD14M). Cross & Morse Timing Belt Catalogue, polyurethane belts: tooth shear resistance table, design limits for maximum belt tension and stock lengths. ContiTech SYNCHROBELT HTD Synchronous Drive Belts catalogue (power ratings, factors, permissible pull) and ContiTech list of dimensions (stock lengths and widths). Gates Industrial Power Transmission catalogue (Synchro-Power PU stock sizes) and Gates TPU Product Catalog (allowable belt force and effective force tables). Always check current figures with the manufacturer.