Tools & calculators
How many slaves can I poll at my target cycle time?
Switch between Modbus RTU and TCP, dial in your baud / block size / cycle target, and see exactly how many slaves a Wiman gateway can serve — plus which model fits.
Bus protocol
Live calculation
Capacity result
Time per read query –ms
Time per slave –ms
Max slaves at target cycle –slaves
Bus utilization at max –%
Bus utilization –%
0% · idle · 50% · healthy · 80% · tight · 100% · saturated
Recommended gateway
View model –
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How this is calculated
The bus timing math, in the open
These are the same formulas our pre-sales engineers use to size a Modbus bus. Every Wiman gateway uses standard Modbus framing — no proprietary tricks — so the math is portable to any RTU or TCP slave you'll meet in the field.
RTU frame sizes
- Modbus RTU read request = 8 bytes (slave id, function, addr hi/lo, qty hi/lo, CRC hi/lo).
- Response = 5 + (N × 2) bytes where N is register count.
- Each UART byte = 10 bits (1 start + 8 data + 1 stop, no parity).
- Tx time = (framing bits / baud) × 1000 ms.
- Slave processing typical = 4 ms added per query.
Per-slave + capacity
- perSlaveMs = (blocks × perQueryMs) + interFrameGap
- maxSlaves = floor((cycleSec × 1000) / perSlaveMs)
- utilization% = (maxSlaves × perSlaveMs) / (cycleSec × 1000) × 100
- TCP path skips serial framing — uses your measured frame latency directly, with 1 ms overhead per slave.
- For a healthy bus, keep utilization under ~80% to leave headroom for retries and bursty event traffic.
RTU + TCP MODES STANDARD MODBUS FRAMING NO VENDOR LOCK-IN BROWSER-ONLY — NO UPLOAD ENGINEERED BY WIMAN
Need help sizing a deployment?
Our engineers will validate the numbers against your real device list and recommend the right gateway.