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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25 calculators

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Resistor Calculator

Decode 4/5/6-band resistor color codes to ohms or reverse-calculate the color bands from any resistance value. Free, instant, and accurate.

★ 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.

★ 4.952K uses

IP Subnet Calculator

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 Calculator

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. Free online calculator with formula guide and step-by-step results.

★ 4.939K uses

Base64 Encoder / Decoder

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. Free, instant, and accurate.

★ 4.946K uses

Token Converter

Estimate token counts for any text across OpenAI (cl100k_base), Claude, Llama 3, and General tokenizers. Free, instant, and accurate.

★ 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.

★ 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

Fluid Flow Rate & Pipe

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 12 models from 6 providers: GPT-5, Claude 4.7, Gemini 3.1, DeepSeek V3, Grok 3, Llama 4. Free, instant, and accurate.

★ 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).

★ 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. Free, instant, and accurate.

★ 4.910K uses

pH Calculator

Calculate pH, pOH, H+ and OH- ion concentrations in aqueous solutions. Enter any known value to get the complete acid-base profile with step-by-step results.

★ 4.954K uses

Nusselt Number

Calculate the Nusselt number from convective heat transfer coefficient, characteristic length, and fluid thermal conductivity. Includes flow regime interpretation.

★ 4.938K uses

Buffer Capacity

Calculate buffer capacity (β) using the Van Slyke equation. Find how much acid or base your buffer can neutralize before pH changes. Includes selection guide.

★ 4.945K uses

Prandtl Number

Calculate the Prandtl number from viscosity, specific heat, and thermal conductivity. Fluid classification for gases, water, oils, and liquid metals included.

★ 4.938K uses

Froude Number

Calculate the Froude number for open channel flow, spillways, and ship hulls. Determine if flow is subcritical, critical, or supercritical with wave celerity.

★ 4.931K uses

Lead Screw

Calculate required torque, mechanical advantage, and power for Acme and ball screw drives. Essential for 3D printer, CNC, and linear actuator design.

★ 4.910K uses

Freezing Point Depression

Calculate freezing point depression using the van't Hoff equation. Find how salt, antifreeze, or any solute lowers the freezing point. Includes molality auto-calculation.

★ 4.915K 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 25 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.