Kelly Calculator

We have developed this Productivity Calculator to help you understand the costs and benefits you might expect from a Kelly Diamond Harrow. By using information from your own farm, you can see the prodcutivity of the selected tools, including recommended horsepower, running costs and expected wear rate. We hope you find this informative.

Please enter your name and email to calculate the results

All fields require user input. Some fields, such as productive efficiency and fuel usage, contain default or assumed values. These default values may be overwritten.

Tractor (HP)
Kelly Model
Chain/Disc type
Soil type:
Speed of operation (mph)
Labor cost ($/hr)
Productive efficiency (%)
Fuel price ($/gal)
Fuel consumption Gallons per hour, leave default or enter your own figure

* Default gal/hour is calculated from your tractor HP.

Currency Adjustment
Custom Exchange Rate

Crop type
Crop Acres sown
Fall passes
Spring passes
Average yield in bu / Acre
Commodity price per bu (in $)

Planter width (feet)
Average start of planting date
Normal planter operating speed (mph)
Average start of harvest date
Expected increase in planter speed (mph)
Expected number of days you can enter
the field earlier than usual by using Kelly

*We expect at least 1mph planting speed increase

Glyphosate application rate (Gallons/Acre)
Expected % improvement in plant
establishment using Kelly
Expected weed kill % from herbicide

*Experience tells us between 5% and 10% is normal

Glyphosate cost per gal. (in $)

The information that you provide may be used by Kelly Engineering to contact you with relevant information about our business, products, and services. We will hold this information for as long as necessary, and may pass it on to our dealers and associates in the interests of providing you with personalised customer service. Your information is your property, and you retain the right to request access, transferral, rectification, and erasure of it, as well as the right to withdraw consent to our use of it and the right to lodge a complaint with a Data Protection Authority (DPA).

  Terms and Conditions:

This calculator is intended to stimulate questions and thinking about the uses of the Kelly Tillage System. Although we have taken great care in researching the formulae and factors used in this calculator, it is to be used for illustrative purposes only. Our assumptions are transparent and supported by many years of field experience. In all instances throughout the calculator you may override our assumptions and use your own. Kelly cannot accept any liability for the use of this information or for the outcome of any decision you make as a result of this calculator.



Planter productivity: Acre per hour
Increase in Planter productivity: Acre per hour
Improved planter productivity result: Acre per hour
Growing season -Days between planting and harvest: Days
Percentage increase in growing season by accessing fields sooner
Percentage increase in production through stand/germination and establishment improvement

Tool Wear

Tool Type:
Total Acres worked each year:
Expected life of the tool in Acres:
Number of years in your program before tool replacement:
Price of a replacement set of tools:
Cost of tool wear per year:


Glyphosate cost per Acre - applied:
Cost of one spray pass over full crop area:
Cost of Kelly for one full pass:
Benefit of one weed kill substitution:
Yield Data
Calculated increase in growing season: (Assumption : 1% increase in growing season = 1% increase in production)
Stand increase: (Assumption : 1% increase in stand establishment = 0.5% increase in production.)
Crop1 Crop2 Crop3 Crop4
Standard yield bu/acre
Revised yield bu/acre
Value of increased yield per acre
Gross value of improvement
Sum of improvement in income

Selected Model Specifications

Horsepower Recommended: Hp
Productivity for Kelly: Acre per hour
Fuel cost: per Acre
Labour cost: per Acre
Working cost of Kelly including labour, fuel and wear: per Acre
Farm size: Acre
Area worked with the Kelly each year: Acre
Total machinery cost per year (Cost per Acre * Acre worked)


Which model can I pull with my tractor?

Your existing Tractor: Hp
Based upon your tractor, soil type and disc selection you could manage a model: with an effective width of ft
To stay ahead of your planter you will need a model: