V-Belt Length Calculator
Pitch length from centre distance and the two sheave diameters, plus the small-sheave arc of contact — pick the right belt first time.
Order the next standard length and adjust the centres — belts come in catalog steps, not custom millimetres. The arc of contact is the quiet killer in compact drives: a big ratio jammed into a short centre distance wraps so little belt around the small sheave that it slips at a fraction of rated power, and tightening it further just cooks the bearings. Catalog power ratings silently assume 180° of wrap.
Formula
Pitch length from centre distance and the two sheave diameters, plus the small-sheave arc of contact — pick the right belt first time. A free machinist & fabrication essentials tool — no sign-up, no upload, instant results in your browser.
About V-Belt Length Calculator
V-Belt Length Calculator computes the governing relationship L = 2C + π(D+d)/2 + (D−d)²/4C ; arc ≈ 180° − 57.3·(D−d)/C live as you type. Order the next standard length and adjust the centres — belts come in catalog steps, not custom millimetres. The arc of contact is the quiet killer in compact drives: a big ratio jammed into a short centre distance wraps so little belt around the small sheave that it slips at a fraction of rated power, and tightening it further just cooks the bearings. Catalog power ratings silently assume 180° of wrap. Defaults are pre-filled with realistic values for this exact scenario, and the worked example substitutes your numbers step by step so the math is never a black box.
How to use V-Belt Length Calculator
- 1Enter your values — Centre distance, Large sheave pitch Ø, Small sheave pitch Ø (sensible defaults are pre-filled).
- 2Read the live results: Belt pitch length, Arc of contact (small sheave).
- 3Check the "with your numbers" line to see L = 2C + π(D+d)/2 + (D−d)²/4C ; arc ≈ 180° − 57.3·(D−d)/C substituted step by step.
- 4Adjust inputs until the scenario matches yours, then copy or share the result.
Why use V-Belt Length Calculator?
- ✓Instant, free and private — every calculation runs client-side in your browser; nothing is uploaded
- ✓Built on the stated formula L = 2C + π(D+d)/2 + (D−d)²/4C ; arc ≈ 180° − 57.3·(D−d)/C with authoritative sources cited on the page (Shigley's Mechanical Engineering Design, 11th ed.; Machinery's Handbook, 31st ed.)
- ✓Order the next standard length and adjust the centres — belts come in catalog steps, not custom millimetres.
- ✓SI ⇄ Imperial toggle converts your inputs in place, so you can work in the units your drawings use
Frequently asked questions
What formula does the v-belt length calculator use?+
It evaluates L = 2C + π(D+d)/2 + (D−d)²/4C ; arc ≈ 180° − 57.3·(D−d)/C, exactly as published. Sources: Shigley's Mechanical Engineering Design, 11th ed.; Machinery's Handbook, 31st ed.. The substituted worked example on the page lets you verify every step against the textbook.
How should I read the result — and how far can I trust it?+
Order the next standard length and adjust the centres — belts come in catalog steps, not custom millimetres. Treat the output as a planning estimate and verify against the governing documents for your project.
When is this calculator the right tool for the job?+
Pitch length from centre distance and the two sheave diameters, plus the small-sheave arc of contact. The arc of contact is the quiet killer in compact drives: a big ratio jammed into a short centre distance wraps so little belt around the small sheave that it slips at a fraction of rated power, and tightening it further just cooks the bearings. For neighbouring scenarios, the related tools below cover the same engine with different presets.
Does it support both metric and imperial units?+
Yes — the SI ⇄ Imperial toggle converts the values already in the fields, preserving the physical quantity, so you can flip mid-calculation without re-entering anything.
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