What inertia ratio is usually targeted for servo systems?

A common practical target is reflected load inertia around 5:1 or lower versus motor inertia for easier tuning.

Can this calculator replace full dynamic simulation?

No. It is a pre-RFQ estimator. Final selection should validate full motion profile, resonance risk, thermal behavior, and controller tuning constraints.

Which inputs improve quote accuracy most?

Motor model, load inertia assumptions, duty cycle, peak torque events, and mounting/interface drawings are the highest-impact inputs.

Tool

Inertia Matching Calculator

Estimate reduction-ratio direction from inertia and torque inputs before finalizing a planetary gearhead RFQ.

This tool supports buyer-side pre-checks for servo integration. For final model freeze, pair this output with full-axis dynamics, mounting constraints, and sample validation criteria.

Input Parameters

Enter motor inertia, load inertia, and torque targets to estimate a practical reduction-ratio range for servo stability and torque margin.

Motor Rotor Inertia

Load Inertia (Output Side)

Motor Rated Torque (N·m)

Load Peak Torque (N·m)

Target Inertia Ratio (Load Reflected / Motor)

Gear Efficiency (0-1)

Practical rule: keep reflected inertia ratio around 5:1 or lower for easier servo tuning. Use this as a pre-RFQ estimate, then validate with full motion profile and mechanism dynamics.

Required Min Ratio

7.44 : 1

Max of inertia and torque constraints.

Inertia-Limited Ratio

2.31 : 1

Based on target inertia ratio 5.

Torque-Limited Ratio

7.44 : 1

Load peak torque vs motor rated torque and efficiency.

Suggested Standard Start

10 : 1

First viable standard ratio from this estimate.

Recommended Standard Ratios

10:115:120:125:130:140:1

Motor inertia: 4.500e-5 kg·m² · Load inertia: 1.200e-3 kg·m²

Candidate Evaluation Table

Ratio	Reflected Inertia (kg·m²)	Inertia Ratio	Available Output Torque (N·m)	Torque Margin	Status
5:1	4.800e-5	1.07	5.71	0.67x	Excellent Inertia ✓ / Torque ✕
7:1	2.449e-5	0.54	8.00	0.94x	Excellent Inertia ✓ / Torque ✕
10:1	1.200e-5	0.27	11.43	1.34x	Excellent Inertia ✓ / Torque ✓
15:1	5.333e-6	0.12	17.14	2.02x	Excellent Inertia ✓ / Torque ✓
20:1	3.000e-6	0.07	22.86	2.69x	Excellent Inertia ✓ / Torque ✓
25:1	1.920e-6	0.04	28.57	3.36x	Excellent Inertia ✓ / Torque ✓
30:1	1.333e-6	0.03	34.29	4.03x	Excellent Inertia ✓ / Torque ✓
40:1	7.500e-7	0.02	45.72	5.38x	Excellent Inertia ✓ / Torque ✓

Need an Engineering Cross-Check?

Send your duty cycle, load profile, and motor details. We can return a ratio recommendation and integration notes for your RFQ.

Inquiry Email

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Guides to Interpret Calculator Output

Use these articles to move from ratio estimate to project-ready architecture and supplier decisions.

How to Match a Servo Motor to a Planetary Gearhead: Inertia Ratio Explained

Detailed method behind reflected inertia logic and first-pass ratio boundaries.

NEMA 23 vs NEMA 34 Gearhead: Which Size for Your Application?

Frame-size implications for torque reserve, thermal behavior, and integration risk.

The Real Cost of Cheap Gearheads: Why Precision Matters in Production

Convert technical assumptions into procurement and repeat-order execution criteria.

Continue Your Selection Workflow

Products for family-level architecture and ratio feasibility.
NEMA Compatibility for frame-size fit-check and interface validation points.
Contact / RFQ to share full duty-cycle data for engineering review.