calc.engineer

Plan and validate network link capacity for homelab workloads. Determine whether a 1G, 2.5G, 10G, or faster link can handle your concurrent streams (VMs, backups, media, iSCSI). Calculates effective bandwidth after TCP/IP overhead, total required bandwidth, utilization percentage, and remaining headroom. Flags saturation at 80% utilization and identifies whether the bottleneck is network or storage. Provides a 1TB transfer time reference and recommends the next link speed upgrade if your current link is saturated. Useful for planning NIC upgrades, switch purchases, and storage network design.

Calculate the cascaded noise figure of a multi-stage receiver chain using the Friis formula. Each stage has a noise figure and gain in dB. The first stage dominates overall system noise, which is why low-noise amplifiers (LNAs) are placed at the front of the chain. Returns total cascaded noise figure, total gain, and equivalent noise temperature. Feeds into link_budget for complete receive-chain sensitivity analysis.

Solves Ohm's Law and the power equation given any two of four electrical quantities: voltage (V), current (I), resistance (R), and power (P). Uses V=IR, P=VI, P=I^2R, and P=V^2/R to derive the missing two values. Fundamental for every circuit design task: sizing resistors, estimating current draw, checking power dissipation, and verifying component ratings. Chain into led_resistor for LED circuits or voltage_divider for bias networks.

Calculate voltage gain and output for operational amplifier circuits in inverting, non-inverting, and differential configurations. For inverting: Av = -Rf/Ri with input impedance equal to Ri. For non-inverting: Av = 1 + Rf/Rg with very high input impedance. For differential: Av = Rf/Ri applied to (V1 - V2). Reports gain in linear and dB, output voltage when input is provided, input impedance, and phase inversion status. Ideal op-amp assumptions (infinite open-loop gain, zero input bias current). Chain from ohms_law for power budgeting or resistor_color_code for component selection.

Calculate the p-value for a z-score or t-statistic. Supports one-tailed (left or right) and two-tailed hypothesis tests using either the standard normal distribution or the Student's t-distribution when degrees of freedom are specified. Returns significance flags at the 0.01, 0.05, and 0.10 alpha levels. Essential for interpreting results from t-tests, z-tests, ANOVA post-hoc comparisons, and regression coefficients. Uses the Abramowitz & Stegun normal CDF approximation and regularized incomplete beta function for the t-distribution.

Turn a SPICE netlist into a fab-ready 2-layer PCB: assigns real footprints (0805, TO-92, DO-35, DIP-8, headers, LED, radial-cap), auto-places components (connectivity-aware; or use your own placement), routes a 2-layer maze router with vias, and VERIFIES the result with DRC (clearance/crossing checks) and ERC (union-find copper connectivity proven against the netlist). Returns the board, routing stats + honest unrouted-net list, DRC violations, ERC net status, a 'manufacturable' flag (true only when DRC+ERC clean and everything routed), SVG layers (top/bottom copper, silkscreen, drill, assembly), and optional Gerber RS-274X + Excellon drill files. Same netlist you simulate with spice_simulate — design, verify, and lay out an entire board through the tool layer. Supply a 'placement' array for production-quality boards; the auto-router is a first-pass best-of-N-seeds.

Estimate PCB component temperatures by solving a thermal resistance network (thermal↔electrical analogy) with the built-in MNA solver. Each component gets a junction node (package θjb from a typical-datasheet table), a local board node coupled to its neighbours through in-plane FR4/copper conduction, and convection to ambient. Computes per-component junction and case temperatures, board extremes, and flags max-junction violations. Runs instantly in-worker; mesh-level CFD via container backend is planned.

Calculate PCB via current-carrying capacity using the IPC-2221 standard. A plated via is a hollow copper cylinder whose cross-sectional area is the annular ring of plating: A = pi * (D - t) * t, where D is the drill diameter and t is plating thickness. The IPC-2221 empirical formula I = k * dT^0.44 * A^0.725 (k=0.048) then gives the maximum current for a given temperature rise. Also computes via barrel resistance from copper resistivity (1.724e-6 ohm-cm) and barrel length (board thickness). When a target current is specified, returns how many parallel vias are needed. Essential for power planes, high-current paths, and thermal via arrays. Chain with trace_width to verify both trace and via can handle the same current.

Calculate what percentage one number is of another. Given a value and a total, returns the percentage, decimal form, and simplified fraction. For example, 3 out of 4 yields 75%, 0.75, and '3/4'. Commonly used for test scores, survey results, financial ratios, completion rates, and unit conversions. Chain with percentage_increase to compare successive measurements or use with test_grade for academic scoring.

Calculate the percentage change between an old value and a new value. Determines whether the change is an increase or decrease, the absolute change, and the percentage change. Essential for financial analysis (stock price changes, revenue growth), scientific measurements (before/ after experiments), performance benchmarks, and population statistics. A positive percentage indicates growth; negative indicates decline. Division by zero (old_value = 0) is handled gracefully.

Calculate total power consumption, electricity cost, and circuit requirements for a homelab. Enter each device's wattage to get daily/monthly/yearly kWh and cost at your local electricity rate. Accounts for cooling overhead via PUE (Power Usage Effectiveness). Shows amperage draw at 120V and 240V and warns if you exceed the NEC 80% continuous load limit on a 15A breaker. Essential for budgeting homelab operating expenses and ensuring your electrical panel can handle the load. Chain output total_watts into cooling_btu for heat load sizing.

Select bypass and bulk decoupling capacitors for IC power supply pins. Computes the target PDN (Power Distribution Network) impedance from supply current, voltage, and allowable ripple using Z_target = V_ripple / I_total. Recommends a ceramic bypass capacitor (high-frequency decoupling, placed closest to IC pins) and a bulk capacitor (low-frequency decoupling, near the regulator). Calculates the ceramic cap's self-resonant frequency assuming typical lead inductance, and checks whether ESR-induced ripple stays within limits. Essential for digital, analog, and mixed-signal PCB design. Chain with lc_resonance to verify the decoupling capacitor's resonant behavior, or with trace_width to size the power trace.

Solve for any side of a right triangle using the Pythagorean theorem (a² + b² = c²). Provide any two of the three sides (a, b, c) and the missing side is computed. Also returns the triangle area (0.5 * a * b), perimeter, and confirms it is a right triangle. Side c is always the hypotenuse. Fundamental to surveying, construction (squaring corners), navigation (distance calculations), physics (vector decomposition), and 3D graphics. Chain with slope_calc for coordinate geometry or square_root for simplified radical answers.

Quick rack space and weight sizing calculator for homelab and small data center racks. Enter your devices with their height in rack units, weight, and wattage to get total utilization, remaining free space, weight totals in lbs and kg, and recommended PDU count based on the NEC 80% continuous load rule (1920W per 20A/120V PDU). Estimates cable management overhead at 2U per 10U of installed gear. Outputs total_watts that chains into power_cost and cooling_btu for full infrastructure planning.

Estimate RAID array IOPS performance and latency for ZFS and traditional RAID configurations. Calculates maximum read IOPS, write IOPS (accounting for write penalty/amplification per RAID level), blended IOPS for a configurable read/write workload mix, and rough per-disk latency. Supports stripe, mirror, raidz1, raidz2, and raidz3. Use with HDD IOPS (~150), SATA SSD (~50000), or NVMe SSD (~100000) to compare RAID topologies and plan storage performance for databases, VMs, media servers, and general homelab NAS workloads. Chains from zfs_capacity.data_disks for integrated capacity+performance planning.

Computes the cutoff frequency, time constant, impedance, and phase shift of a first-order RC filter. Supports both lowpass and highpass topologies. The cutoff frequency is f = 1/(2*pi*R*C) where the signal is attenuated by 3 dB. The time constant tau = R*C governs transient response — the capacitor reaches 63.2% of its final value after one tau. Use for anti-aliasing before ADCs, DC blocking, noise filtering, and signal conditioning. Chain from voltage_divider to design filtered bias networks.

Decodes 4-band or 5-band resistor color codes into resistance value, tolerance, and min/max range. Accepts an ordered array of color names (left-to-right as printed on the resistor body). Supports standard EIA color codes including gold and silver multiplier/tolerance bands. Outputs the nominal resistance in ohms, a human-readable formatted value (e.g. '4.7kΩ'), tolerance percentage, and the min/max resistance range. Chain into ohms_law or led_resistor for circuit analysis.

Converts compensation between annual salary, monthly pay, weekly pay, and hourly wage. Accepts any of the four pay periods as input and derives all others. Uses configurable hours per week (default 40) and weeks per year (default 52). Daily rate assumes an 8-hour workday; monthly is annual divided by 12. Useful for comparing job offers quoted in different pay periods, freelance rate-setting, and budgeting. Chain from sales_tax to see how many hours a purchase costs.

Calculates total cost including sales tax for a purchase. Given a unit price, tax rate percentage, and optional quantity, computes the subtotal (price times quantity), the tax amount rounded to two decimal places, and the final total. Useful for estimating purchase costs across US states and municipalities with different tax rates, comparing pre-tax and post-tax prices, and budgeting. Chain into salary_to_hourly to see how many work-hours a purchase represents.

Convert any number to scientific notation and engineering notation. Returns the coefficient, exponent, a formatted string with Unicode superscripts (e.g. '3.14 × 10²'), and engineering notation where the exponent is a multiple of 3. Useful for expressing very large or very small values compactly, common in physics, electronics (picofarads, gigahertz), and astronomy. Accepts output from sig_figs and log_calc for precision-aware formatting.

Count significant figures in a number and optionally round to N significant figures. Accepts the number as a string to preserve trailing zeros (e.g. '1.200' has 4 sig figs). Applies standard sig fig rules: leading zeros do not count, trailing zeros after a decimal point count, trailing zeros before a decimal point are treated as significant. Also returns the number in scientific notation. Essential for laboratory measurements, error analysis, and maintaining proper precision in chained calculations.

Calculate the slope, y-intercept, line equation, angle, and distance between two points in a 2D Cartesian plane. Given coordinates (x1, y1) and (x2, y2), computes slope (rise/run), y-intercept, the equation in slope-intercept form (y = mx + b), angle in degrees relative to the x-axis, and Euclidean distance. Handles vertical and horizontal lines as special cases. Useful for surveying, civil engineering grade calculations, linear regression visualization, and physics kinematics problems.

Computes LoRa link SNR margin by comparing received power against the noise floor and the spreading-factor-dependent demodulation threshold from the Semtech SX1276 datasheet. Calculates receiver noise floor from thermal noise (-174 dBm/Hz), channel bandwidth, and receiver noise figure. Returns margin in dB and a boolean link-OK indicator. Use to validate whether a LoRa or Meshtastic link will reliably decode packets. Accepts rx_power from link_budget tool output for end-to-end chain analysis.

Calculates total daily energy consumption from an appliance list — the critical first step before sizing solar panels or batteries. Enter each appliance with its wattage, hours of daily use, and quantity. Outputs total daily kWh (with configurable safety margin for surge and inrush current), peak simultaneous wattage, and recommended inverter VA rating per NEC 125% continuous load rule. Feeds directly into solar_sizing (daily_kwh) and battery_autonomy (daily_kwh). Essential for residential, RV, cabin, and off-grid system design.

Calculates solar system return on investment, payback period, and levelized cost of energy (LCOE). Models year-by-year savings accounting for panel degradation, utility rate inflation, federal Investment Tax Credit (ITC), state rebates, and annual maintenance. Outputs net cost after incentives, payback year, total lifetime savings, ROI percentage, and LCOE in cents/kWh. Essential for residential and commercial solar financial analysis, installer proposals, and comparing solar vs. grid economics over a 25-year system lifetime.

Sizes an off-grid solar power system by calculating the number of panels and battery bank capacity required for a given daily energy consumption. Accounts for system losses (inverter, wiring, charge controller), battery depth-of-discharge, and autonomy days for cloudy weather. Outputs panel count, total panel wattage, battery capacity in kWh and Ah, and minimum charge controller amperage (with 25% safety margin per NEC 690.8). Supports 12V, 24V, and 48V system architectures. Use for cabin, RV, telecom tower, and remote IoT deployments.

Run a SPICE circuit simulation directly in the worker. Accepts a standard SPICE netlist and performs operating-point (.op), DC sweep (.dc), AC frequency sweep (.ac), or transient (.tran) analysis using a built-in modified-nodal-analysis engine with Newton-Raphson nonlinear solving. Supports R, L, C, V, I sources (DC/AC/SIN/PULSE), diodes, BJTs (Ebers-Moll), MOSFETs (Shichman-Hodges level 1), controlled sources (E/G), .param expressions, .subckt/X hierarchical subcircuits, .measure and .four (Fourier/THD), and a built-in parts library (reference 2n3904/2n2222/1n4148/1n5819/2n7000/tl072/lm358/led_red etc. by name and the model is auto-injected), up to 150 components. Returns voltage vectors for all circuit nodes (magnitude + phase for AC). Use spice_template to generate netlists from parameterized templates.

Generate a complete SPICE netlist from a parameterized template. Supports common circuit topologies: low-pass RC filter, voltage divider, common emitter amplifier. Returns a ready-to-simulate netlist string that can be passed directly to spice_simulate. Use this when an agent needs to construct a circuit from high-level parameters without writing raw SPICE syntax. Feeds into spice_simulate for AC/DC/transient analysis.

Calculates area and perimeter for common shapes — rectangle, circle, or triangle — in both imperial and metric units. Returns area in square feet, square meters, and acres, plus perimeter in feet and meters. For rectangles: area = length * width, perimeter = 2*(length + width). For circles: area = pi * r^2, perimeter = 2 * pi * r. For triangles: area = 0.5 * base * height, perimeter approximated as base + height + sqrt(base^2 + height^2). Useful for real estate, flooring, landscaping, and construction estimates.

Compute the square root of a non-negative number. Returns the decimal result, whether the input is a perfect square, and a simplified radical form (e.g. '√12' simplifies to '2√3'). For integer inputs, factors are extracted from under the radical sign. Useful for geometry (diagonal/hypotenuse calculations), statistics (standard deviation from variance), signal processing (RMS values), and general algebra. Chain with pythagorean_theorem for triangle side calculations.

Calculates optimal solar panel string and MPPT configuration based on panel electrical specs, inverter/charge-controller MPPT limits, and site temperature extremes. Applies temperature coefficients to determine Voc at minimum temperature (cold) and Vmp at maximum temperature (hot), then computes the safe range of panels per string, maximum parallel strings, and total array wattage. Prevents over-voltage damage in winter and under-voltage MPPT dropout in summer. Essential for NEC 690.7 compliant residential and commercial solar design.

Calculate IPv4 subnet details from CIDR notation. Parses a CIDR block (e.g. 192.168.1.0/24) and returns the network address, broadcast address, subnet mask, wildcard mask, first and last usable host addresses, total and usable host counts, prefix length, and classful IP class (A/B/C/D/E). Essential for homelab network planning, VLAN segmentation, firewall rule design, and understanding address space allocation. Handles special cases for /31 point-to-point links (RFC 3021) and /32 host routes.

Calculate maximum TCP throughput using the Bandwidth-Delay Product (BDP) formula. Given link bandwidth and round-trip latency, computes the BDP (maximum in-flight data), achievable throughput with a given TCP window size, link utilization percentage, and recommended window size for full utilization. Critical for diagnosing slow transfers over high-latency links (WAN, VPN, satellite), tuning TCP buffers, and understanding why a 1Gbps link may only deliver 25Mbps with default 64KB windows. Applies to iperf testing, WAN optimization, and network capacity planning.

Calculates a test or exam grade from the number of correct answers and total questions. Returns the percentage score, letter grade, points missed, and GPA points. Supports US grading (A/B/C/D/F with 4.0 GPA scale), UK grading (First/2:1/2:2/Third/Fail), and percentage-only mode. US thresholds: A>=90, B>=80, C>=70, D>=60, F<60. UK thresholds: First>=70, 2:1>=60, 2:2>=50, Third>=40, Fail<40. Useful for students checking scores and teachers computing class statistics.

Estimate steady-state thermal behaviour of a rectangular enclosure (server rack, electronics housing, equipment cabinet) using a lumped-parameter energy balance with natural-convection and radiation correlations, or forced-flow air energy balance. Accepts enclosure dimensions, heat source positions and wattages, and airflow configuration. Returns temperature extremes, estimated hotspot location, airflow velocity summary, and overall thermal resistance. Runs instantly in-worker; a full CFD container backend is planned for mesh-level detail.

Calculates timing parameters for the ubiquitous NE555 / LM555 timer IC in astable (free-running oscillator) and monostable (one-shot pulse) modes. In astable mode, computes frequency, period, duty cycle, and HIGH/LOW durations from R1, R2, and C using f = 1.44 / ((R1 + 2·R2) · C). In monostable mode, computes pulse width from R and C using t = 1.1 · R · C. Standard 555 astable duty cycle is always >50%; for 50% duty cycle use a diode across R2. Useful for generating clock signals, PWM, delays, and debounce circuits. Chain from ohms_law for power calculations or resistor_color_code for component selection.

Convert between Unix timestamps and human-readable date/time formats. Accepts Unix epoch (in seconds or milliseconds), ISO 8601 strings, or 'now' for the current time. Returns both Unix seconds and milliseconds, ISO 8601 UTC string, date and time components, day of the week, relative time description ('2 hours ago'), and past/future indicator. Auto-detects whether a numeric input is seconds or milliseconds based on magnitude. Essential for debugging logs, API timestamps, cron scheduling, and time zone conversions.

Calculate tip and split a restaurant bill among multiple people. Given a bill amount, tip percentage, and number of diners, returns the tip amount, total with tip, per-person share, and effective tip percentage. Supports rounding up to the nearest whole number for convenience. Defaults to 18% tip for 1 person. Currency-agnostic — works with any monetary unit.