Engineering Calculators — Free Online Tools | TheCalcUniverse

Free Engineering Calculators

Browse our collection of free online engineering calculators. Each tool includes the formula, step-by-step instructions, and educational content to help you understand the math behind the numbers. No signup required — just enter your values and get instant results.

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19 calculators

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Resistor

Decode 4/5/6-band resistor color codes to ohms or reverse-calculate the color bands from any resistance value. Includes tolerance range, temperature coefficient, and closest E-series match.

★ 4.946K uses

Electricity Cost

Calculate the energy cost of any electrical appliance. Pick from 20 common appliance presets or enter custom wattage, usage hours, and electricity rate. Projects daily, monthly, and yearly costs.

★ 4.952K uses

IP Subnet

Calculate network address, broadcast address, usable host range, and total hosts for any IPv4 subnet. Includes binary representation and IP class detection.

★ 4.953K uses

Bandwidth

Calculate file transfer times based on connection speed. Includes TCP overhead simulation and clear bit vs byte distinction (Mbps vs MB/s).

★ 4.953K uses

Password Gen

Generate cryptographically secure passwords with customizable length and character types. Includes passphrase mode, entropy calculation, strength meter, and estimated crack time. Uses Web Crypto API.

★ 4.939K uses

Base64

Encode text to Base64 or decode Base64 back to text instantly. Supports text and file input with live encoding and one-click copy.

★ 4.917K uses

URL Encode

Encode text for safe URL transmission or decode URL-encoded strings. Shows character mappings for special characters.

★ 4.946K uses

Token Converter

Estimate token counts for any text across OpenAI (cl100k_base), Claude, Llama 3, and General tokenizers. See token/character ratio, read time, generation time, and API cost estimates.

★ 4.938K uses

Ohm's Law

Calculate voltage, current, resistance, or power using Ohm's Law. Enter any two known electrical values to solve for the unknown.

★ 4.946K uses

Voltage Drop

Calculate voltage drop over a wire run based on AWG gauge, wire length, and current. Checks compliance with the NEC 3% recommended maximum.

★ 4.924K uses

Wire Gauge

Find the correct AWG wire gauge for any electrical circuit based on current, conductor material, insulation rating, and conduit fill. References NEC ampacity tables.

★ 4.910K uses

Gear Ratio

Calculate output RPM, output torque, or gear ratio for any gear system. Supports speed reduction, overdrive, and compound gear train analysis.

★ 4.910K uses

MTBF Calculator

Calculate Mean Time Between Failures (MTBF), system reliability at a specific mission time, and expected number of failures for reliability engineering.

★ 4.918K uses

Flow Rate

Calculate pipe flow velocity, volumetric flow rate, or required pipe diameter using the continuity equation. Supports GPM and metric units.

★ 4.953K uses

AI Token Pricing

Compare token pricing across GPT-4o, GPT-4o-mini, Claude 3.5 Sonnet/Haiku, and Gemini 1.5 Pro/Flash. Estimate per-request, monthly, and annual costs with DAU scaling.

★ 4.925K uses

Crypto Hash

Generate cryptographic hashes locally in your browser using SHA-256, MD5, SHA-1, SHA-384, SHA-512, and Keccak-256 (SHA-3). Zero-knowledge â€” no data is sent to any server.

★ 4.910K uses

Cookie Consent

Generate GDPR-compliant cookie consent banners with customizable position, layout, and color theme. Get ready-to-use HTML/CSS code for your website.

★ 4.930K uses

Rate Limit Calculator

Calculate API throughput including requests per second, bandwidth requirements, daily capacity, and burst limits. Supports AWS API Gateway, Cloudflare, Nginx, and custom server configurations with a traffic flow visualization.

★ 4.910K uses

pH Calculator

Calculate pH, pOH, and concentrations of Hâº and OHâ» ions in aqueous solutions. Enter any value â€” pH, [Hâº], or [OHâ»] â€” to get the complete acid-base analysis with substance classification. Essential for chemistry students, lab work, and science education.

★ 4.954K uses

About Engineering Calculators

From electrical engineering to mechanical systems, our engineering calculators help professionals and students solve real-world problems with precision.

Browse our curated collection of engineering calculators below. Each tool includes detailed formulas, educational content, and real-time results. Use the 19 calculators in this category to make informed decisions, solve problems, and get accurate answers instantly.

Ohm law and voltage drop calculations

Gear ratio, flow rate, and wire gauge tools

MTBF reliability analysis

Engineering unit converters

Frequently Asked Questions

How do I calculate voltage drop for a long wire run?

Voltage drop depends on wire length, conductor material, gauge, and current. The voltage drop calculator does this automatically — enter your wire type, gauge, length, and expected load. It tells you the voltage drop and whether it stays within the recommended 3% threshold for branch circuits.

What is MTBF and how is it calculated?

MTBF stands for mean time between failures, a reliability metric for repairable systems. Divide total operating time by the number of failures. For example, 10 units running 1,000 hours each with 2 failures gives a 5,000-hour MTBF. The MTBF calculator also computes failure rate and availability.

How do I determine the right gear ratio?

Divide the number of teeth on the driven gear by the teeth on the drive gear. A higher ratio increases torque but reduces speed, and vice versa. The gear ratio calculator lets you input both gears and shows the resulting speed, torque, and mechanical advantage.

How do I estimate AI API costs from token counts?

LLM providers charge per token with separate rates for input and output. Count tokens in your prompt and expected response, then multiply by the per-token rate. The AI token pricing calculator does this — select your model, enter token counts, and see cost per request plus volume projections.