Developer Calculators

OpenAI Cost Calculator

Enter your token counts and model pricing to get an instant cost breakdown. Works with GPT-4o, o1, GPT-3.5, and any per-token LLM provider.

429 Too Many Requests: Causes and Fixes

A 429 is the server telling you to slow down, not that your request was malformed. This page explains what it means, how to read the headers that come with it, and what to do next.

Cron Next Run Calculator

Instantly calculate the next run times for any cron expression. Paste your schedule, set a start time, and see exactly when your cron job will fire.

QPS Calculator

Enter your total request count and time window to calculate average and peak QPS instantly. Built for backend engineers sizing APIs, rate limits, and infrastructure.

Throughput Calculator

Enter your total requests, time window, and average response size to instantly calculate throughput in RPS and MB/s. Built for API engineers and backend developers planning system capacity.

Payload Size Calculator

Instantly estimate the byte size of your API request or response payload. Enter your average record size and record count to see total payload, gzip estimate, and daily bandwidth at a glance.

HTTP Request Size Calculator

Estimate the total byte size of any HTTP request — method, URL, headers, and body combined. Built for developers debugging gateway limits, API quotas, and network bandwidth.

Thread Pool Size Calculator

Enter your CPU count, utilization target, and I/O wait ratio to get the recommended thread pool size. Built on the Brian Goetz formula used in Java Concurrency in Practice.

Worker Queue Throughput Calculator

Enter your worker count, task duration, and queue size to instantly calculate throughput in tasks per second and queue drain time. Built for backend engineers sizing job queues, thread pools, and message brokers.

Retry Backoff Calculator

Instantly compute exponential backoff delays for every retry attempt. Tune your initial delay, multiplier, and cap to build a retry strategy that avoids thundering herd while staying within latency budgets.

Timeout Calculator

Enter your P99 latency and safety multiplier to get a recommended timeout value and total deadline with retries. Works for any HTTP API, database, or microservice call.

Event Processing Rate Calculator

Enter your worker count, per-event processing time, and total event volume to calculate pipeline throughput and queue drain time. Works with Kafka, SQS, RabbitMQ, and any worker pool.

Message Queue Delay Calculator

Enter your queue depth, consumer throughput, and per-message overheads to instantly calculate total end-to-end message delay. Works with RabbitMQ, Kafka, SQS, and any queue-based system.

Batch Processing Time Calculator

Enter your item count, processing rate, and number of workers to instantly estimate total batch job duration. Works for data pipelines, ETL jobs, API batches, and any parallel workload.

API Pagination Limit Calculator

Enter your total record count, page size, and rate limit to instantly calculate how many API requests you need and how long a full data sync will take.

Token Bucket Rate Limit Calculator

Enter your bucket capacity, refill rate, and request cost to instantly see whether a request is allowed, how long to wait if blocked, and your steady-state maximum throughput.

Leaky Bucket Rate Calculator

Instantly calculate effective throughput, request drop rate, and bucket fill time for leaky bucket rate limiting. Designed for API engineers sizing their rate-limit configuration.

Session Size Calculator

Estimate the total token size of an LLM API session and see how much of your context window it consumes. Built for developers sizing chat sessions, agents, and multi-turn API calls.

JSON Size Calculator

Paste any JSON to see its exact byte size and KB. Validates syntax in real time — no backend, no sign-up.

SQL Query Cost Estimator

Enter the data scanned per query and your service's per-TB price to get an instant cost estimate. Works with BigQuery, Athena, Redshift Spectrum, and any per-TB-scan billing model.

Pagination Performance Calculator

Enter your dataset size, page size, and target page number to instantly compare offset vs cursor pagination query times. See exactly how much slower deep pages get with OFFSET.

Index Size Calculator

Estimate how much disk space a database index will consume given your row count, key size, fill factor, and page size. Works for B-tree indexes on PostgreSQL, MySQL, and most relational databases.

Compression Ratio Calculator

Enter your original and compressed file sizes to instantly calculate the compression ratio and space savings. Works with ZIP, gzip, Brotli, zstd, and any other format.

Latency Budget Calculator

Distribute your total response-time SLA across every service layer and instantly see how much headroom remains. Built for backend engineers designing latency-sensitive systems.

Cache Hit Rate Calculator

Enter your total requests and cache hits to instantly see your hit rate, miss rate, and how many requests are reaching your origin server.

Little's Law Calculator: L = λW Explained

L = λW relates how many things are inside a system to how fast they arrive and how long they stay. This page explains what that means, why it holds so widely, and where applying it gives a confident wrong answer.

Bandwidth Cost Calculator

Enter your monthly data transfer volume and per-GB price to get an instant bandwidth cost estimate. Works with AWS, GCP, Azure, Cloudflare, and any pay-per-GB provider.

Storage Cost Calculator

Estimate your monthly and total cloud or on-prem storage bill in seconds. Enter your data volume, price per GB, and how many months you need.

Data Transfer Cost Calculator

Estimate your cloud egress bill in seconds — enter your data volume, per-GB rate, and free tier allowance. Works for AWS, GCP, Azure, and any provider that charges per GB.

API Response Time Estimator

Estimate how long your API endpoint takes to respond by breaking response time into network latency, server processing, payload transfer, and middleware overhead. Built for backend engineers diagnosing slow endpoints and setting realistic SLO targets.

File Upload Time Calculator

Enter your file size and upload speed to instantly estimate how long your upload will take. Accounts for real-world protocol overhead so results match what you see in practice.

Download Speed Calculator

Enter your file size and connection speed to instantly calculate how long a download will take. Works for any file type — software, video, backups, or datasets.

TLS Handshake Time Estimator

Enter your network RTT and TLS version to instantly estimate HTTPS handshake overhead. Works for TLS 1.2, TLS 1.3, and 0-RTT session resumption.

CDN Cost Calculator

Estimate your monthly CDN bill from data transfer volume and request count. Works with AWS CloudFront, Cloudflare, Fastly, and any per-GB CDN provider.

Lambda Cost Calculator

Enter your Lambda function's memory, average duration, and monthly invocation count to get an instant cost breakdown. Works with AWS Lambda and any provider using GB-second billing.

CPU Usage Estimator

Enter your request rate, per-request CPU time, and core count to instantly estimate CPU utilization. Useful for capacity planning, auto-scaling thresholds, and load-test analysis.

Memory Usage Calculator

Estimate the total RAM required for any dataset or in-memory data structure. Accounts for per-item size, runtime overhead, and replica count.

Cache TTL Impact Calculator

Estimate cache hit rate, origin request reduction, and monthly bandwidth savings based on TTL, request rate, and unique object count. Adjust the inputs to tune your CDN or application cache for optimal performance.

Log Storage Cost Calculator

Enter your daily log volume, retention window, and compression ratio to get an instant monthly storage cost estimate. Works with S3, GCS, Azure Blob, Elasticsearch, and any GB-priced store.

Base64 Size Calculator

Enter the original byte count to see the exact Base64-encoded size and overhead. Useful for JWT sizing, cookie limits, and inlined image planning.

Hash Collision Probability Calculator

Enter the number of items and your hash function's bit size to instantly calculate the probability of at least one collision. Covers CRC32, SHA-256, and any fixed-width hash.

Encryption Overhead Calculator

Enter your plaintext size and algorithm to instantly see ciphertext size, overhead bytes, and encryption time. Works for AES-128-GCM, AES-256-GCM, AES-256-CBC, and ChaCha20-Poly1305.

Regex Performance Calculator

Paste any regex pattern to instantly estimate its time complexity, detect catastrophic backtracking (ReDoS), and calculate execution time at your target scale.

Kubernetes Resource Calculator

Enter your replica count, CPU requests, and memory requests to instantly see total cluster resource consumption. Includes CPU and memory limits so you can right-size nodes before deploying.

Pod Capacity Calculator

Enter your node size and pod resource requests to instantly see how many pods fit — and which resource is your scheduling bottleneck.

Disk IOPS Calculator

Calculate disk IOPS from seek time, RPM, block size, and transfer rate. Works for HDDs, SSDs, and NVMe drives — enter your drive specs and get an instant result.

RAID Capacity Calculator

Enter your disk count, disk size, and RAID level to instantly calculate usable storage capacity and fault tolerance. Covers RAID 0, 1, 5, 6, and 10.

Freshness Markers Calculator

Enter how long ago your content was updated and its half-life to get an instant freshness score. Use the result to prioritise which pages need a refresh.

CRA Compliance Score Calculator

Score your product's EU Cyber Resilience Act compliance across five mandatory domains in under a minute. Built for software vendors, manufacturers, and security leads preparing for CRA enforcement.

CVE Exposure Calculator

Enter a CVE's CVSS score, exploit status, and asset criticality to get a weighted exposure score from 0–100. Built for security engineers who need to prioritise patches across their infrastructure.

Patch SLA Calculator

Enter a CVE discovery date and severity level to instantly calculate your patch deadline, days remaining, and SLA compliance status. No sign-up required.

SBOM Coverage Calculator

Enter your component counts to get a weighted SBOM coverage score in seconds. Built for security engineers, compliance teams, and DevSecOps pipelines.

OTA Compliance Checker

Enter your fleet size and update counts to instantly check OTA compliance against your target. See your compliance gap and how long it will take to close it at your current rollout rate.

Device Lifecycle Compliance Calculator

Enter your fleet size, EOL device counts, and compliance target to instantly measure your device lifecycle compliance rate. See your at-risk exposure and how many devices need refresh.

Firmware Risk Score Calculator

Quantify firmware security risk across your device fleet in seconds. Enter CVE count, patch lag, SBOM coverage, and internet exposure to get a scored risk rating from 0 to 100.

Vulnerability Response Time Calculator

Enter a discovery date, remediation date, and SLA target to instantly see whether your team met the patch deadline. Works for Critical (1-day), High (7-day), Medium (30-day), and Low (90-day) severity classifications.

Encryption Coverage Calculator

Enter your total assets and how many are encrypted at rest and in transit to get an instant coverage score. Ideal for security audits, compliance reviews, and gap analysis.

EU Device Compliance Quiz

Answer 6 yes/no questions and instantly see your EU device compliance readiness score. Covers CE marking, Cyber Resilience Act (CRA), and the key security controls required for EU market entry.