System · DWG LS-023

Plant unit converter & pulley speed calculator

Pick a tool below. Convert units, work simple geometry, or get driven shaft RPM from pulley sizes — then use those numbers in the lube calculators.

Published method (unit definitions)Last reviewed 14 Oct 2026

Source: NIST Special Publication 811

Drive / pulley speed

Belt or chain ratio (no slip). Same units on both sheaves — diameter or tooth count.

Driver (motor / input) RPM

Driver sheave size

Driven sheave size (same unit)

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n_driven = n_driver × (size_driver / size_driven). Slip and compound drives not included.

Surface speed ↔ shaft speed

Convert feet per minute (belt, roll, or surface speed) to RPM and back. Needs the rolling diameter — same relationship used on drums and for vibration order analysis.

Surface speed (FPM)

Shaft speed (RPM)

Diameter (pitch / roll / sheave)

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RPM = FPM ÷ (π × diameter in feet). FPM = π × D_ft × RPM. Use pitch diameter for sheaves; roll/drum OD for surface speed. No slip assumed.

Oil density / gravity

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SG = 141.5 / (°API + 131.5). lb/gal × 119.83 ≈ kg/m³. Water ≈ 8.328 lb/gal @ 60°F.

Length

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Area

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Shape

Length

Width

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Volume

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US liquid gallons (not Imperial). 1 US gal = 231 in³ = 3.785 L.

Shape

Length

Width

Height

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Full vessel volume only. Partial-fill horizontal tanks not included.

Pressure / stress

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Temperature

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Force / load

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