Load Balancer Distribution Calculator
Calculate per-backend request distribution for round-robin and weighted load balancing.
Inputs
Leave matching backend count for weighted distribution; equal weights = simple round-robin
Requests per Backend (Equal Split)
2,500.00req/s
Highest-Loaded Backend
3,333.33req/s
Lowest-Loaded Backend
1,666.67req/s
Sum of Weights
6
Step by step
Values used
Total Requests per Second = 10,000; Number of Backends = 4; Backend Weights (optional, comma-separated) = 1, 1, 2, 2
Equal (round-robin) distribution
requests_per_backend = total_requests / number_of_backends
Weighted distribution
backend_requests = total_requests × (weight / sum_of_weights)
Requests per Backend (Equal Split)
= 2,500.00 req/s
Highest-Loaded Backend
= 3,333.33 req/s
Lowest-Loaded Backend
= 1,666.67 req/s
Sum of Weights
= 6
How it works
Simple round-robin load balancing divides total request rate evenly across all backends: requests_per_backend = total / backends. Weighted distribution instead allocates traffic proportionally to each backend's assigned weight (typically reflecting relative capacity, e.g. a backend twice as powerful gets a weight of 2 versus 1 for standard instances): backend_rps = total × (weight / sum_of_weights). Weighted round-robin is standard practice when backend instances have heterogeneous capacity, ensuring more capable instances handle proportionally more traffic instead of being artificially limited to an equal share.
Formulas
Equal (round-robin) distribution
requests_per_backend = total_requests / number_of_backends
Weighted distribution
backend_requests = total_requests × (weight / sum_of_weights)
Frequently Asked Questions
When should I use weighted instead of simple round-robin?
Use weighted distribution whenever backends have different capacities — e.g. mixing larger and smaller instance types, or gradually shifting traffic during a blue-green deployment — so more capable (or more trusted) backends receive proportionally more traffic than smaller ones.
Does round-robin guarantee perfectly even real-world load?
Not necessarily — round-robin distributes requests evenly by count, but if request processing times vary (some requests are much heavier than others), backends can still end up unevenly loaded in terms of actual resource consumption despite receiving an equal request count.
How do health checks affect this distribution model?
This calculator assumes all backends are healthy and receiving traffic. In practice, load balancers continuously run health checks and remove unhealthy backends from rotation, which increases the effective load on the remaining healthy backends beyond what this static calculation shows.
What's the difference between this and least-connections load balancing?
Round-robin and weighted round-robin distribute based on a fixed ratio regardless of current backend state. Least-connections (and similar dynamic algorithms) instead route each new request to whichever backend currently has the fewest active connections, adapting in real time to actual load rather than a static split.