TLS Handshake Rate Calculator

Calculate sustainable TLS handshake rate from core count, key algorithm and resumption rate, plus the round trips setup costs.

About TLS Handshake Rate Calculator

Handshake capacity is set by asymmetric signing throughput, which depends entirely on the key algorithm and size. Resumption replaces that operation with a symmetric key derivation costing roughly a twentieth as much, so a high resumption rate multiplies effective capacity. Handshake rate — not throughput — is what falls over during a thundering-herd reconnect after a deployment, and TLS 1.3 halves the user-visible setup latency on top of that.

Formula

TLS Handshake Rate

handshake rate = cores × operations per core ÷ ((1 − resumption rate) + 0.05 × resumption rate), since a resumed handshake costs about 5% of a full one.

costFactor: Average cost of a handshake relative to a full one
roundTrips: 1 for TLS 1.3, 2 for TLS 1.2, before any application byte moves

Worked example

With the default values below, TLS Handshake Rate Calculator returns Sustainable Handshake Rate of 597,015. Change any input above and every figure here is recalculated in your browser.

Inputs used

CPU cores dedicated to TLSaccepts 1–512 cores: 8 cores
Certificate key typeone of RSA 2048, RSA 4096, ECDSA P-256, ECDSA P-384: ECDSA P-256
Handshakes resumedaccepts 0–100 %: 70 %
TLS versionone of TLS 1.3 (1-RTT handshake), TLS 1.2 (2-RTT handshake): TLS 1.3 (1-RTT handshake)
Network round-trip timeaccepts 0.1–2,000 ms: 20 ms

Results

Sustainable Handshake Rate: 597,015 handshakes/s
Capacity if Every Handshake Were Full: 200,000 handshakes/s
Signing Operations per Core: 25,000 ops/s
Round Trips Before Application Data: 1
Handshake Latency: 20.0 ms

Step by step

1Values used
2TLS Handshake Rate
3Sustainable Handshake Rate= 597,015 handshakes/s
4Capacity if Every Handshake Were Full= 200,000 handshakes/s
5Signing Operations per Core= 25,000 ops/s
6Round Trips Before Application Data= 1
7Handshake Latency= 20.0 ms

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is TLS Handshake Rate calculated?

handshake rate = cores × operations per core ÷ ((1 − resumption rate) + 0.05 × resumption rate), since a resumed handshake costs about 5% of a full one. Handshake capacity is set by asymmetric signing throughput, which depends entirely on the key algorithm and size. Resumption replaces that operation with a symmetric key derivation costing roughly a twentieth as much, so a high resumption rate multiplies effective capacity.

Why does TLS Handshake Rate matter?

Handshake rate — not throughput — is what falls over during a thundering-herd reconnect after a deployment, and TLS 1.3 halves the user-visible setup latency on top of that.

What values do I need to enter?

This calculator takes 5 inputs: CPU cores dedicated to TLS, Certificate key type, Handshakes resumed, TLS version, Network round-trip time. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.