Build a software business case
Compare software cost, adoption risk, expected benefit, TCO, and payback before you ask for budget.
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Business / ROISaaS ROI CalculatorEstimate software return, net benefit, and payback from SaaS costs, time savings, and revenue lift.MortgageMortgage Payment CalculatorEstimate principal, interest, taxes, insurance, HOA, and total monthly payment.BudgetingMonthly Cashflow PlannerPlan monthly inflows, outflows, cash buffer, shortfall, surplus, scenarios, and a copyable cashflow summary.ConversionsLength ConverterConvert feet, meters, inches, yards, miles, centimeters, millimeters, and kilometers.EngineeringPower ConverterConvert watts, kilowatts, horsepower, metric horsepower, BTU/hour, and foot-pounds per second.Digital & ComputingNumber Base ConverterConvert whole numbers between bases 2 through 36, including binary, decimal, octal, hexadecimal, and base 36.
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Get the number — and what it means.
Run what-if checks for business cases, mortgages, budgets, debt, measurements, engineering specs, digital formats, network ranges, solar systems, dates, geometry, and project materials. CalcShelf shows the headline answer first, then explains the result in plain English so you can decide what to try, verify, or change next.
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🧠 Plain-English result notes
🔒 No saved inputs
Popular first steps
Start with the job, then choose the calculator.
Start with the real-world question. The links jump straight to calculators that explain the answer, not just spit out a number.
Price work or products
Work backward from launch cost, income goals, package scope, delivery capacity, unit cost, margin, and markup.
Plan monthly money flow
Check cash timing, buffer gaps, monthly budget categories, savings targets, and payoff options before the month gets noisy.
Plan a network
Sketch VLANs, sites, zones, subnets, gateways, DHCP ranges, and host capacity.
Plan solar or backup power
Start from loads, then size panels, batteries, inverter, charge controller, wire, roof fit, backup runtime, and payback.
Estimate project materials
Choose the right paint, drywall, drywall finishing, framing lumber, sheathing panels, insulation, roofing, siding, house wrap/weather barrier, soffit/fascia, gutters/downspouts, trim/baseboard, quarter round/shoe molding, door/window casing, deck-board, stair-stringer/tread, fence, paver, gravel, topsoil, landscape fabric, rebar, concrete block, post-hole concrete, tile, flooring, concrete, or mulch estimator before buying supplies.
Material estimatorsDrywallDrywall finishingRoofingGutters/downspoutsSoffit/fasciaSidingHouse wrap / WRBStair stringers/treadsTrim/baseboardQuarter round/shoe moldingDoor/window casingCrown moldingCaulk/sealantSheathing panelsInsulationDeck boardsFraming lumberFencePaversGravelTopsoilLandscape fabricRebarConcrete blockConcrete footingPost-hole concreteTilePaintFlooringConcrete
Browse by decision type
Start with the kind of decision you’re making.
Each shelf is organized around a real job, with calculator copy written for normal humans instead of spreadsheet archaeologists.
Business decisions
ROI, launch, payback, pricing, margin, CAC, and growth calculators for business cases and quick sanity checks.
Use when you need to justify a purchase, plan a launch, price work, or compare a campaign.
Buying plannerSaaS ROIPayback period
Open shelf → Mortgage planning
Payment, payoff, affordability, refinance, rent-vs-buy, amortization, and Canada-specific mortgage tools.
Use when the sticker price is not enough and the monthly reality matters.
PaymentCanada mortgageRent vs buy
Open shelf → Money planning
Cashflow, budget, savings, debt payoff, emergency fund, net worth, and credit-card payoff calculators.
Use when you want the next number: surplus, payoff date, savings target, or runway.
Cashflow plannerMonthly budgetDebt payoff
Open shelf → Measurements & conversions
Fast converters for height, distance, area, speed, fuel economy, data, weight, volume, temperature, and cooking measurements.
Use when you just need the unit answer without a bloated converter page.
HeightDistanceArea
Open shelf → Engineering & electrical
Power, horsepower, torque, voltage, pressure, energy, force, density, and flow-rate calculators for technical checks.
Use when you need a quick spec conversion or simple electrical/mechanical sanity check.
PowerTorqueVoltage
Open shelf → Digital & computing
Binary, decimal, hex, base conversion, text/ASCII/Unicode, bits, bytes, storage units, and IPv4 converters.
Use when you need a code-friendly conversion without a heavyweight tool.
Binary/hexASCIIBits/bytes
Open shelf → Networking utilities
CIDR, subnet masks, IP ranges, wildcard masks, subnet splitting, MAC address formatting, and common port lookup.
Use when network math needs to be right before you touch routing or firewall rules.
CIDRIP rangesPorts
Open shelf → Solar planning
Solar load, panel count, series/parallel wiring, wire gauge, battery bank, inverter, charge controller, roof fit, tilt, backup, and payback calculators.
Use before buying panels, batteries, controllers, inverters, or cable so the system math holds together.
LoadPanelsBattery
Open shelf → Time & date planning
Days-between-dates, age, and elapsed-time calculators for deadlines, trips, shifts, and planning.
Use when the question is “how long?” or “how many days?”
Date differenceAgeDuration
Open shelf → Geometry basics
Area, perimeter, circumference, volume, and surface-area calculators for common shapes.
Use when a quick measurement turns into a shape problem.
RectangleCircleCylinder
Open shelf → Construction materials
Paint, drywall, drywall finishing, framing lumber, sheathing panels, insulation, roofing, siding, house wrap/weather barrier, soffit/fascia, gutters/downspouts, decking, stair stringers/treads, pavers, gravel, topsoil, flooring, concrete, and mulch estimators for practical project planning.
Use before the hardware-store run so you buy roughly the right amount.
DrywallSheathingPaint
Open shelf → Compare scenarios
Change one input and see the delta: payment, interest saved, payoff time, ROI, or total cost.
Understand the result
Headline numbers come with plain-English explanations, next steps, and watch-outs so you know what the result actually means.
Come back when numbers change
Use the same shelf again when a quote, rate, payment, budget, or project assumption changes.
Popular tools
Start with a useful one
These are the calculators people are most likely to need first.