Free preliminary sizing tool
Gearbox ratio, torque and inertia calculator
Estimate output torque and speed through reduction gearing, plus load inertia reflected to the motor. Check assumptions before choosing a gearbox.
No registration is needed to calculate. Review the method, assumptions and worked example before using the figures.
Enter your calculation inputs
The initial values are an illustrative example. Replace them with your application figures. Calculations run in your browser and do not contact an AI service.
Method and assumptions
n_out = n_in / i; T_out = T_in × i × η; J_reflected = J_load / i²
Use a reduction ratio of at least 1, expressed as input revolutions per output revolution. Enter efficiency as a percentage and load inertia at the gearbox output in kg·m². The tool estimates forward motoring relationships at one operating point.
Illustrative worked example
Illustrative inputs: 2 Nm, 3,000 rpm, 10:1 reduction, 90% efficiency and 0.02 kg·m² load inertia give 18 Nm, 300 rpm and 0.0002 kg·m² reflected load inertia. These numbers do not establish that a particular gearbox can carry the duty.
What the result does not establish
Calculated torque is not a gearbox rating. Check continuous, peak, emergency-stop and bearing loads, duty, speed, backlash, stiffness and lifetime. Reflected load inertia excludes the gearbox, coupling and motor inertia. Reverse efficiency and backdrivability are not calculated.
These are general preliminary calculations, not an engineer-approved design, customer case study or product recommendation. Use the exact manufacturer's ratings and installation conditions for final selection.
Kollmorgen: application sizing guide · Gearbox selection guide
UK engineering team · Product sourcing · Supply support
Ask for a component selection using these figures
Send your part number or describe what the machine needs to do. We connect your requirement with experienced UK engineering and procurement support to help you get the right products, pricing and supply options. Your matched provider can take the enquiry through quotation and ordering to delivery and after-sales support.
- Source original parts or assess suitable alternatives
- Get pricing, lead times and a defined supply proposal
- One enquiry for components, complete axes and ongoing support
No obligation to buy. Choose the quick form below or use the full configurator on this page. Add what you know; an engineer can help with the details.
Need help choosing? Build a specification →Other motion calculations
Servo RMS torque calculator
Calculate time-weighted RMS torque, peak magnitude and cycle time from torque-and-time segments. Carry the figures into a motor sizing enquiry.
Linear actuator force and screw torque calculator
Estimate one upward-motion load case, screw torque, screw speed and mechanical output power. Prepare the figures for an actuator selection enquiry.
Technical resources and checklists · Content and calculation policy
Spec builder
Build your specification
Select the products and performance you need. Our UK engineering team can use your specification to help source the right components, pricing and supply options. See your summary before adding contact details.
Already know the part number? Use the quick enquiry form. You can configure a requirement below without registering.
- 1Products
- 2Performance
- 3Environment
- 4Volumes
- 5Your spec
What are you specifying?
Select everything you need. A motor, drive and gearbox can be specified together as one axis.
UK engineering input · A route to buying the right products
From your enquiry to products, delivery and support
Specify Motion helps turn a part number or application into a purchasing enquiry. We provide recommendations and connect your requirement with a relevant engineering or procurement provider for product selection, pricing, sourcing and supply.
- Tell us what you needSend a code or configure the application, quantities and timing.
- Reach a relevant providerAccess experienced UK engineering input and a suitable procurement route.
- Review the quotationYour provider confirms the products, price, compatibility checks and supply terms.
- Order with delivery and support agreedConfirm delivery, warranty and after-sales arrangements with the contracting provider.
You choose whether to proceed with the provider and should carry out your own checks. Website and introduction service terms.