Software & Networks Calculators
Queueing, throughput, storage, and the classical laws of computing.
- CIDR Subnet CalculatorTurn an IPv4 address and prefix length into network, broadcast, host range, and usable host count.network = IP AND mask , mask = 0xFFFFFFFF << (32 − prefix) , broadcast = network OR ~mask , hosts = 2^(32−prefix) − 2
- TCP Bandwidth-Delay Product & WindowSize the TCP receive window for a fat pipe — get the bandwidth-delay product and whether window scaling is required.BDP = bandwidth × RTT , max throughput = window / RTT , scaling required when BDP > 65 535 bytes
- Amdahl's Law SpeedupPredict the ceiling on speedup when you only parallelize (or accelerate) part of a workload.S(N) = 1 / [ (1 − p) + p/N ] , S_max = 1 / (1 − p)
- Gustafson-Barsis Scaled SpeedupEstimate parallel speedup when the problem grows with the processor count — the optimistic counterpoint to Amdahl.S(N) = s + (1 − s)·N = N − s·(N − 1)
- M/M/1 QueueAverage wait, queue length, and utilization for a single-server queue with Poisson arrivals and exponential service.ρ = λ/μ, W = 1/(μ−λ), Wq = ρ/(μ−λ), L = ρ/(1−ρ), Lq = ρ²/(1−ρ)
- Little's Law (L = λW)Relate items in a system, arrival rate, and time-in-system — solve for whichever one you don't have.L = λ · W
- Shannon-Hartley Channel CapacityMaximum error-free bit rate for a channel given its bandwidth and signal-to-noise ratio.C = B · log₂(1 + S/N), S/N = 10^(SNR_dB / 10)
- Hamming Code Parity BitsFind how many parity bits a SEC Hamming code needs for a given number of data bits, plus the overhead.smallest k such that 2^k ≥ m + k + 1 , SECDED adds one overall parity bit → k+1 , n = m + k
- Base64/Hex Encoding OverheadSize a payload after Base64, Base32, or hex encoding — exact RFC 4648 byte counts for link budgets, MTU checks, and storage estimates.Base64: 4·⌈n/3⌉ Base64 unpadded: ⌈4n/3⌉ MIME: +2·⌈len/76⌉ for CRLF Base32: 8·⌈n/5⌉ Hex: 2n
- RAID Usable CapacityUsable storage, efficiency, and fault tolerance for RAID 0/1/5/6/10 given drive count and size.RAID0: N·S , RAID1: 1·S , RAID5: (N−1)·S , RAID6: (N−2)·S , RAID10: (N/2)·S
- Serial/Parallel System MTBFRoll up component failure rates into a system MTBF for series or active-parallel redundancy.Series: λ_sys = Σλᵢ, MTBF = 1/λ_sys , Parallel(n identical): MTBF = (1/λ)·Σ_{k=1}^{n} 1/k , R_series = ∏Rᵢ, R_parallel = 1 − ∏(1−Rᵢ)
- Utilization Law (ρ = λS)Find how busy a server or resource is from its arrival rate and mean service time.ρ = λ · S / c (single server: ρ = X · S = λ · S)
- Effective Memory Access TimeBlend cache-hit and miss-penalty times into the average access time your CPU actually sees.AMAT = Hit time + Miss rate · Miss penalty
- Bloom Filter False-Positive RateSize a Bloom filter — false-positive probability, optimal hash count, and bits-per-element for a given m, n, k.p ≈ (1 − e^(−k·n/m))^k k_opt = (m/n)·ln 2 p_min ≈ 0.6185^(m/n)
- TLS Record OverheadWire-byte cost of pushing application data through the TLS record layer — records, tags, headers, and goodput efficiency.TLS 1.3 AEAD: 5 (header) + 1 (content type) + tag per record · TLS 1.2 GCM: 5 + 8 (explicit nonce) + 16 · TLS 1.2 CBC: 5 + 16 (IV) + 32 (HMAC) + pad(1–16)
- JWT Payload Byte SizePredict the on-the-wire size of a signed JWT before it blows past your cookie or proxy header limits.len_b64url(n) = ⌈4n/3⌉ (unpadded), token = len(header) + len(payload) + len(sig) + 2 dots
- Token Bucket Rate LimiterSize a token bucket for an API or network path — sustained rate, burst allowance, and how long a burst can run before it throttles.tokens(t) = min(C, tokens₀ + r·t − Σcost) , burst = tokens₀ / (arrival·cost − r) , sustained = r / cost