Load testing starts free; paid tiers run $19 to $149 a month

01Three numbers at the 95th percentile, never an average

The original treated latency, “efficiency” and percentiles as separate aspects. They are one report. Latency is read at the 95th percentile, because the mean hides the one user in twenty who waited eight seconds. Throughput is the requests per second the system sustained while that 95th percentile stayed inside the target. Error rate is the share of requests that failed or timed out; a test that stops before it moves has not found the ceiling.

The browser-side targets are published. Google’s Core Web Vitals ask for the largest content to paint within 2.5 seconds, an interaction to be answered within 200 milliseconds and layout shift to stay under 0.1, each at the 75th percentile of real page loads.⁵ A server-side load test needs a tighter budget than 2.5 seconds, because the network, the CDN and the browser spend part of it before your code runs.

02What the tools cost, as of September 2026

Grafana Cloud k6 is free for 500 virtual-user hours a month; Pro is a $19 monthly platform fee that includes those hours and then meters from $0.15 a virtual-user hour; Enterprise starts at a $25,000 annual commitment.¹ BlazeMeter’s free tier runs 50 users for 20 minutes; Basic is $149 billed monthly or $1,188 a year for 1,000 concurrent users and one-hour tests.² Gatling Enterprise Basic is €99 a month for up to 60,000 virtual users, one hour of testing and one load generator.³ OpenText Performance Engineering, formerly LoadRunner, has a free Community licence for 50 virtual users; every paid edition is quoted and licensed by virtual user.⁴

The arithmetic that matters is the shape of the meter. k6 charges for hours of simulated users, so a short test of a festival-sale peak is cheap and a long soak test is not. BlazeMeter and Gatling sell a ceiling of users and test time that you pay for whether you reach it or not. OpenText sells the virtual user itself across 180-plus protocols, which suits an SAP or Oracle estate and few others.⁴ For a web or API product, a team that already writes JavaScript will usually find k6 the cheapest route to a defensible number.

03If you are buying this in India

For a bank or NBFC this is not optional. The RBI’s Information Technology Governance, Risk, Controls and Assurance Practices Directions, 2023, issued 7 November 2023 and in force from 1 April 2024, require a regulated entity to assess the capacity of its IT resources at least annually, against past peak usage and projected needs, with the IT Strategy Committee reviewing it.⁶ A load test is how that assessment gets a number. The second rule bites everyone: copying production customer records into a load generator is processing personal data under the DPDP Act, 2023, whose Rules were notified on 13 November 2025 with the security and breach duties in force from 13 May 2027.⁷ Generate synthetic data instead. Every price here is a USD or euro list; an Indian reseller invoice adds 18% GST.