calc.engineer is an MCP server with 89 tools an agent can call, among them attenuator_pi, attenuator_tee, battery_autonomy. It answers at https://calc.engineer/mcp over streamable HTTP, and it listed its tools to an anonymous client, so no sign-in was needed for that. Our probes reached it 6 of 6 times since 10 September 2026; the last check, on 19 October 2026, succeeded.
88 free engineering calculators: RF link budgets, LoRa/Meshtastic, PCB, solar, homelab. Keyless.
Description as the publisher wrote it.
| Tool | What it does |
|---|---|
attenuator_pi | Design a Pi-topology resistive attenuator pad. Given a desired attenuation in dB and characteristic impedance (default 50 ohm), computes the three resistor values for a symmetrical Pi-pad network. The Pi attenuator uses two shunt resistors Inputs: attenuation_db, z0_ohm |
attenuator_tee | Design a Tee-topology resistive attenuator pad. Given a desired attenuation in dB and characteristic impedance (default 50 ohm), computes the three resistor values for a symmetrical T-pad network. The Tee attenuator uses two series resistor Inputs: attenuation_db, z0_ohm |
battery_autonomy | Calculates how many days a battery bank can sustain loads without solar input — critical for off-grid and backup power sizing. Accounts for depth of discharge, round-trip efficiency (lithium vs lead-acid), minimum state of charge, and optio Inputs: daily_kwh, battery_kwh, dod, round_trip_efficiency, min_soc_pct, avg_solar_contribution_pct |
battery_charge_time | Estimates battery charge time given capacity in mAh, charge current in mA, charger efficiency, and initial state of charge. Accounts for real-world charging losses (typically 80-90% efficient) to produce time in hours and minutes, energy re Inputs: capacity_mah, charge_current_ma, efficiency, initial_soc_pct, voltage_v |
battery_life | Calculates battery runtime and energy capacity given cell capacity in mAh, nominal voltage, and average current draw. Accounts for real-world discharge efficiency (Peukert-adjacent derating) to produce effective capacity, total energy in Wh Inputs: capacity_mah, voltage, current_draw_ma, efficiency |
bmi_calculator | Calculate Body Mass Index (BMI) from weight and height using the WHO standard formula. Supports metric (kg/cm) and imperial (lbs/inches) units. Returns the BMI value, WHO classification (Underweight, Normal, Overweight, Obese Class I-III), Inputs: weight, height, unit |
capacitor_charge | Calculates RC capacitor charge timing, energy storage, and transient voltages. Given resistance, capacitance, supply voltage, and optional initial voltage, computes the RC time constant (τ = R×C), time to reach standard charge thresholds (6 Inputs: resistance_ohm, capacitance_f, v_supply, v_initial, v_target |
channel_utilization | Estimates Meshtastic or LoRa mesh channel utilization percentage based on node count, message rate, and per-packet airtime. Determines how much of the shared radio channel is occupied and computes the maximum number of nodes before exceedin Inputs: nodes, messages_per_hour_per_node, airtime_ms, max_duty_cycle_pct |
circumference | Calculate the circumference and area of a circle given either a radius or diameter. Provide one or both; if both are given, radius takes precedence. Returns circumference (C = 2πr), area (A = πr²), and both radius and diameter for completen Inputs: radius, diameter |
compound_interest | Calculates compound interest growth over time using the formula A = P(1 + r/n)^(nt). Given a principal, annual rate, duration in years, and compounding frequency, returns the future value, total interest earned, effective annual rate (APY), Inputs: principal, annual_rate_pct, years, compounds_per_year, monthly_contribution |
confidence_interval | Calculate the confidence interval for a sample mean. Given a sample mean, sample size, standard deviation, and confidence level, computes the margin of error, lower and upper bounds, critical z-score, and standard error. Supports finite pop Inputs: sample_mean, sample_size, standard_deviation, confidence_level, population_size |
cooling_btu | Estimate the cooling load (BTU/hr) for a homelab or server closet based on equipment wattage, room dimensions, insulation quality, and solar exposure. All electrical power converts to heat — this tool calculates equipment heat output, envel Inputs: total_watts, room_length_ft, room_width_ft, room_height_ft, insulation, ambient_temp_f |
date_difference | Calculate the difference between two dates in days, weeks, months, years, and business days. Accepts dates in YYYY-MM-DD format. Returns the absolute difference (order doesn't matter) plus a flag indicating whether the end date is in the fu Inputs: start_date, end_date |
dbm_convert | Convert a power level in dBm to milliwatts, watts, dBW, and RMS voltage across a given impedance. dBm is the standard unit for RF power referenced to 1 milliwatt. This tool is essential when interfacing datasheets (which use dBm) with circu Inputs: dbm, impedance_ohm |
dipole | Calculate physical dimensions of a dipole antenna for a given frequency. Returns half-wave or quarter-wave element length in metres, feet, and inches. A half-wave dipole is the most common resonant antenna with approximately 2.15 dBi gain. Inputs: freq_mhz, type |
duty_cycle_budget | Calculates LoRa duty cycle budget for EU868, US915, AS923, and AU915 regulatory regions. Computes maximum messages per hour, minimum transmission interval, and effective data rate under regional duty cycle constraints. EU868 and AS923 enfor Inputs: airtime_ms, region |
eirp_compliance | Checks EIRP (Effective Isotropic Radiated Power) compliance against regional regulatory limits for LoRa and Meshtastic operation. Computes EIRP from transmit power, antenna gain, and cable loss, then compares against FCC (US, 36 dBm), ETSI Inputs: tx_power_dbm, antenna_gain_dbi, cable_loss_db, region, custom_limit_dbm |
exponent_calc | Compute the result of raising a base to an exponent (base^exponent). Handles positive and negative exponents, fractional exponents, and zero. Returns the numeric result and a scientific notation string for very large or very small results. Inputs: base, exponent |
fresnel_zone | Calculate the Fresnel zone radius at the midpoint of a radio link. Given frequency in MHz, link distance in kilometres, and zone number (1-5), returns the Fresnel zone radius in metres and feet, plus the 60% clearance threshold used in prac Inputs: freq_mhz, dist_km, zone_number |
fspl | Calculate free-space path loss (FSPL) in decibels using the ITU-R P.525 standard formula. Given a frequency in MHz and distance in kilometres, returns the expected signal attenuation in an ideal line-of-sight radio link with no obstacles, r Inputs: freq_mhz, dist_km |
generator_offset | Compares total cost of ownership between a fuel generator and a solar+battery system over a configurable time horizon. Calculates yearly and cumulative costs for generator-only, solar-only (amortized), and hybrid scenarios. Accounts for fue Inputs: generator_fuel_cost_per_gallon, generator_consumption_gph, generator_hours_per_day, generator_maintenance_per_1000hrs, solar_system_cost_usd, solar_daily_kwh_produced |
heatsink_cfd | Analyze a forced-convection fin-array heatsink using established channel-flow correlations (developing laminar Nusselt, fin efficiency tanh(mH)/mH, parallel-plate friction). Computes base-to-air thermal resistance, pressure drop, base and f Inputs: base_length_m, base_width_m, base_height_m, fin_count, fin_height_m, fin_thickness_m |
hex_converter | Convert numbers between hexadecimal, binary, decimal, and octal bases. Accepts any base as input (prefix 0x for hex, 0b for binary, 0o for octal, or plain decimal) and returns all four representations simultaneously. Also reports bit width, Inputs: value |
impedance_match | Designs an L-network impedance matching circuit between two real impedances at a given frequency. Computes the required shunt and series reactive components (inductor and capacitor) to transform the source impedance to the load impedance. T Inputs: source_ohm, load_ohm, freq_mhz |
inverter_sizing | Size a DC-to-AC inverter for off-grid solar, battery backup, or mobile power systems. Computes the required continuous VA rating from total load watts and power factor, estimates surge capacity for motor-starting loads (3-7x rated power), a Inputs: continuous_watts, surge_watts, largest_load_watts, system_voltage, power_factor, efficiency |
lc_resonance | Calculates the resonant frequency of an LC circuit, along with optional Q factor and bandwidth when series resistance is provided. The resonant frequency f0 = 1/(2*pi*sqrt(L*C)) is where inductive and capacitive reactances cancel. Used for Inputs: inductance_h, capacitance_f, resistance_ohm |
led_resistor | Calculates the current-limiting resistor for driving one or more LEDs in series from a DC supply. Computes the exact resistance from R = (Vsupply - n*Vf) / I, then selects the nearest E24 standard resistor value. Reports the actual current Inputs: supply_voltage_v, led_forward_v, led_current_ma, led_count |
link_budget | Compute a full RF link budget from transmitter power, frequency, distance, and antenna gains. Calculates EIRP, free-space path loss (ITU-R P.525), received power at the receiver, and link margin relative to an optional receiver sensitivity Inputs: tx_dbm, freq_mhz, dist_km, tx_gain_dbi, rx_gain_dbi, rx_sensitivity_dbm |
loan_amortization | Computes a full loan amortization schedule given principal, annual interest rate, and term in months. Returns the fixed monthly payment, total interest, total payments, and a month-by-month breakdown of principal vs interest. Supports optio Inputs: principal, annual_rate_pct, term_months, extra_payment |
log_calc | Compute logarithms of a positive number in any base. Returns the custom-base logarithm, natural logarithm (ln), common logarithm (log10), and binary logarithm (log2). Useful for signal processing (decibel calculations), information theory ( Inputs: value, base |
lora_airtime | Calculates LoRa packet time-on-air using the Semtech AN1200.13 formula. Computes symbol duration, preamble time, payload symbol count, effective data rate, and the minimum transmission interval for 1% duty cycle compliance. Essential for ca Inputs: sf, bw_khz, cr, payload_bytes, preamble_symbols, explicit_header |
lora_param_optimizer | Recommends optimal LoRa spreading factor, bandwidth, and TX power based on target range, terrain, and optimization priority. Iterates through all SF (7-12) and BW (125/250/500 kHz) combinations, computing achievable range, airtime, data rat Inputs: target_range_km, terrain, max_payload_bytes, priority, region, antenna_gain_dbi |
lora_range_estimate | Estimates LoRa maximum communication range by computing the free-space path loss (FSPL) link budget and applying terrain-dependent correction factors. Calculates total link budget from transmit power, antenna gains, and receiver sensitivity Inputs: tx_dbm, freq_mhz, tx_gain_dbi, rx_gain_dbi, rx_sensitivity_dbm, terrain |
lora_sensitivity | Calculates LoRa receiver sensitivity from spreading factor, bandwidth, and noise figure using the Semtech SX1276 datasheet SNR thresholds. Computes the noise floor from thermal noise density (-174 dBm/Hz), channel bandwidth, and receiver no Inputs: sf, bw_khz, noise_figure_db |
mah_to_wh | Converts battery capacity from milliamp-hours (mAh) to watt-hours (Wh), kilowatt-hours (kWh), and joules (J) given the nominal cell voltage. This is the most common battery unit conversion needed when comparing cells rated in mAh (e.g. 1865 Inputs: capacity_mah, voltage_v |
meshtastic_power | Calculates Meshtastic node power consumption and battery runtime using device-specific power profiles and firmware role-based duty cycling. Models sleep, RX, and TX current draw for Heltec V3, RAK WisBlock, T-Beam, T-Beam Supreme, and Stati Inputs: device, channel_preset, battery_mah, battery_voltage, messages_per_hour, gps_enabled |
meshtastic_range | Estimates Meshtastic node communication range using real hardware profiles and firmware channel presets. Combines device-specific TX power and antenna gain (Heltec V3, RAK WisBlock, T-Beam, T-Beam Supreme, Station G2) with firmware modem pr Inputs: device, channel_preset, terrain, antenna_gain_dbi, tx_power_dbm, sf |
microstrip | Calculate PCB microstrip trace width for a target characteristic impedance using the Hammerstad-Jensen closed-form equations. Given target impedance (Z0), substrate dielectric constant (er), substrate height, and copper weight, returns the Inputs: z0_ohm, er, height_mm, copper_oz, freq_mhz |
network_bandwidth | 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 re Inputs: link_speed_gbps, concurrent_streams, stream_bandwidth_mbps, protocol_overhead_pct, storage_throughput_mbps |
noise_figure_cascade | 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 a Inputs: stages |
ohms_law, op_amp_gain, p_value, pcb_layout, pcb_thermal, pcb_via_current, percentage_calc, percentage_increase, power_cost, power_supply_decoupling, pythagorean_theorem, rack_capacity, raid_iops, rc_filter, resistor_color_code, salary_to_hourly, sales_tax, scientific_notation, sig_figs, slope_calc, snr_margin, solar_load_audit, solar_roi, solar_sizing, spice_simulate, spice_template, square_footage, square_root, string_sizing, subnet_calculator, tcp_throughput, test_grade, thermal_enclosure, timer_555, timestamp_converter, tip_calculator, trace_width, unit_convert, ups_runtime, voltage_divider, voltage_drop, vswr, watts_to_amps, wavelength_freq, wire_ampacity, wire_gauge, wireguard_mtu, zfs_capacity, zfs_ram
Every block below points at https://calc.engineer/mcp. Pick your client and copy.
claude mcp add --transport http calc-engineer https://calc.engineer/mcp
{
"mcpServers": {
"calc-engineer": {
"command": "npx",
"args": ["-y", "mcp-remote", "https://calc.engineer/mcp"]
}
}
}{
"mcpServers": {
"calc-engineer": {
"url": "https://calc.engineer/mcp"
}
}
}{
"servers": {
"calc-engineer": {
"type": "http",
"url": "https://calc.engineer/mcp"
}
}
}{
"context_servers": {
"calc-engineer": {
"url": "https://calc.engineer/mcp"
}
}
}{
"mcpServers": {
"calc-engineer": {
"serverUrl": "https://calc.engineer/mcp"
}
}
}{
"mcpServers": {
"calc-engineer": {
"url": "https://calc.engineer/mcp"
}
}
}name: calc.engineer
version: 0.0.1
schema: v1
mcpServers:
- name: calc.engineer
type: streamable-http
url: https://calc.engineer/mcp{
"mcpServers": {
"calc-engineer": {
"httpUrl": "https://calc.engineer/mcp"
}
}
}{
"mcpServers": {
"calc-engineer": {
"type": "http",
"url": "https://calc.engineer/mcp"
}
}
}{
"mcpServers": {
"calc-engineer": {
"url": "https://calc.engineer/mcp"
}
}
}goose://extension?url=https%3A%2F%2Fcalc.engineer%2Fmcp&type=streamable_http&id=calc-engineer&name=calc.engineer
It answered our last check on 19 October 2026 in 562 ms. Over 6 checks since 10 September 2026 it answered 6. Status here comes from Neuronto's own probes, not from the publisher.
Yes. It is published by calc.engineer and served from calc.engineer, the vendor's own domain: https://calc.engineer/mcp.
89, as returned by the server's own tools/list on 11 September 2026: attenuator_pi, attenuator_tee, battery_autonomy, battery_charge_time, battery_life, bmi_calculator, capacitor_charge, channel_utilization, and 81 more.
It answered our last check on 19 October 2026 in 562 ms. Over 6 checks since 10 September 2026 it answered 6.
Put the server under mcpServers in ~/.cursor/mcp.json with the URL https://calc.engineer/mcp. The exact JSON is above, with the same setup for Claude Code, Claude Desktop, VS Code, Windsurf, Zed, Gemini CLI and the rest.
It listed its tools to an anonymous client, so reading the tool list needs no key. Individual tools can still ask for credentials in their own inputs.
Publisher: engineer.calc. Endpoint host: calc.engineer. ARD identifier: urn:air:engineer.calc:mcp:calc.
First indexed 10 September 2026. The tools are exactly what the server returned; nothing on this page
is inferred from its name. Ranking in Neuronto search is never for sale.