Why scale by clean-conversion rate?

Off-the-shelf drivers cover most legacy devices. The rest need custom register maps, byte-order fixes, or scripting; scaling captures that cost.

What is a fair cost per device?

Often 250 dollars for simple Modbus serial and 1500 dollars for complex BACnet or proprietary serial including custom driver work.

Should I include the gateway cost in the per-device line?

Yes if the gateway maps one-to-one to a device. If many devices share a gateway, fold the gateway cost into the fixed adder and use a smaller per-device line for engineering only.

How do I model a phased conversion?

Run the calculator per phase using the device count for that phase. Sum the totals.

IIoT, SCADA & Edge Connectivity calculator

Protocol Conversion Cost Calculator

Estimate protocol conversion cost. Enter the count of legacy devices to convert (Modbus, DNP3, BACnet, serial), conversion cost per device (gateway plus engineering), the share that converts cleanly without custom driver work, and a fixed program engineering adder. The calculator returns the variable conversion cost and the loaded total.

What this calculator does

Estimate the loaded cost of legacy protocol conversion (Modbus, DNP3, BACnet, serial) to OPC UA or MQTT from the count of devices to convert, conversion cost per device (gateway hardware plus engineering), the share that converts cleanly without driver custom work, and a fixed program engineering adder.
Use it when an OT integrator is sizing a brownfield protocol conversion project to bring legacy serial or Modbus devices onto OPC UA or MQTT for an MES or unified namespace.
It returns the loaded cost of converting a block of legacy devices to OPC UA or MQTT, broken into variable per-device cost and a fixed program adder.

Formula used

Variable protocol conversion cost = devices × cost per device × clean-conversion rate
Total protocol conversion cost = variable cost + fixed program engineering adder

Inputs explained

Legacy devices to convert: Use the count of legacy Modbus, DNP3, BACnet, or serial devices being brought onto OPC UA or MQTT.
Conversion cost per device: Use gateway cost (Kepware seat, Red Lion, Moxa, ProSoft) plus integrator engineering per device (typical 250 to 1500 dollars per device including testing).
Clean-conversion rate: Use the share that converts cleanly with off-the-shelf drivers (typical 70 to 90 percent; the rest need custom register maps or scripting).
Fixed program engineering adder: Use the program-level engineering: namespace standards, naming, conversion architecture, and overall PM.

How to use the result

Use it before a brownfield connectivity sprint, when scoping a unified namespace project, or when comparing gateway platforms head-to-head.
It assumes the legacy devices are accessible and powered. Devices behind locked panels or no power need a separate access plan.

Common questions

Why scale by clean-conversion rate? Off-the-shelf drivers cover most legacy devices. The rest need custom register maps, byte-order fixes, or scripting; scaling captures that cost.
What is a fair cost per device? Often 250 dollars for simple Modbus serial and 1500 dollars for complex BACnet or proprietary serial including custom driver work.
Should I include the gateway cost in the per-device line? Yes if the gateway maps one-to-one to a device. If many devices share a gateway, fold the gateway cost into the fixed adder and use a smaller per-device line for engineering only.
How do I model a phased conversion? Run the calculator per phase using the device count for that phase. Sum the totals.

Last reviewed 2026-05-12.