Guides
EverydayCalc guides
EverydayCalc guides explain the assumptions, formulas, examples, and planning rules behind our calculators. Use these guides when you want to understand the numbers before making a purchase, planning a project, comparing options, or sharing an estimate.
How to use this guide library
- Start with a featured guide if you are new to the topic.
- Use category links to jump to the type of estimate you need.
- Open the matching calculator when you are ready to enter exact numbers.
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These broad guides are good first stops for common home, cost, moving, aquarium, finance, and classroom planning questions.
Finance
How Much Do I Need for Retirement? Target, 401(k) Growth, and Savings Gap
Build a retirement target from spending and other income, project 401(k) growth, and solve the monthly savings gap without mixing the three decisions.
Finance
FIRE vs. Coast FIRE: Which Retirement Number Are You Solving For?
Compare a FIRE date with a Coast FIRE balance using one spending target while keeping ongoing contributions, inflation, and claim limits explicit.
Home Air
How to Choose a Dehumidifier Size
Learn how room size, dampness, ceiling height, and cool basement conditions affect dehumidifier sizing.
Costs
Complete Electricity Cost Calculator Guide
A complete guide to estimating electricity cost from watts, kWh, hours, rates, and monthly usage.
Home Improvement
Complete Paint Coverage Guide
A complete guide to estimating paint gallons, wall area, coats, coverage, waste, and beginner painting supplies.
Moving
Complete Moving Box and Supplies Guide
A complete guide to moving boxes, truck size, storage units, tape, supplies, and moving cost planning.
Finance
How credit card interest is calculated: APR, daily rate, and average daily balance
See how a card issuer can turn APR and daily balances into interest for one billing period, and why your statement may not match a quick estimate.
Aquarium
Complete Aquarium Heater Sizing Guide
A complete guide to aquarium heater wattage, tank gallons, temperature rise, placement, and safety checks.
Moving GuidesPlan boxes, truck size, supplies, storage, and move-cost assumptions before packing starts. 6 guides
Most useful
Moving
How Many Moving Boxes Do You Need?
Estimate moving boxes by bedrooms, occupants, storage, and packing style before ordering supplies.
Moving
How Many Moving Boxes for a 2 Bedroom Apartment?
Estimate boxes for a 2 bedroom apartment by occupants, closets, kitchen items, books, storage, and packing style.
Moving
What Size Moving Truck for a 2 Bedroom Apartment?
Choose a moving truck size for a 2 bedroom apartment by furniture volume, stairs, packing density, and trip distance.
Moving
First Apartment Moving Supplies Checklist
Plan boxes, tape, packing paper, labels, cleaning supplies, and open-first essentials for a first apartment move.
Moving
How Many Boxes for a One Bedroom Apartment?
Estimate moving boxes for a one bedroom apartment based on occupants, closets, books, kitchen items, and packing style.
Moving
How Many Boxes for a Three Bedroom House?
Estimate moving boxes for a three bedroom house with closets, garage storage, kitchen items, books, and fragile packing.
Home Air GuidesUnderstand humidity, dampness, room size, air purifier CADR, ventilation, and equipment sizing assumptions. 24 guides
Most useful
Home Air
Complete Home Humidity Guide
A complete guide to indoor humidity, dehumidifier sizing, humidifier sizing, basement moisture, and comfort ranges.
Home Air
What Size Dehumidifier Do I Need?
Choose a dehumidifier pint size by room area, dampness, humidity level, and basement conditions.
Home Air
What Size Dehumidifier for 500 Sq Ft?
Estimate dehumidifier pint size for a 500 square foot room, bedroom, or basement by comparing dampness, ceiling height, and moisture sources.
Home Air
What Size Dehumidifier for 1,000 Sq Ft?
Estimate dehumidifier pint size for a 1,000 square foot basement, open room, or large area.
Home Air
What Size Dehumidifier for 500 Sq Ft Basement?
Estimate the right dehumidifier size for a 500 square foot basement and check when to round up for damp conditions.
Home Air
What Size Dehumidifier for 1000 Sq Ft Basement?
Estimate dehumidifier pint size for a 1,000 square foot basement with damp, musty, or humid conditions.
Home Air
Best Humidity Level for a House
Understand comfortable indoor humidity ranges and when a house may feel too dry, humid, or musty.
Home Air
CADR vs Room Size: How to Size an Air Purifier
Understand CADR, room volume, and air changes per hour before choosing an air purifier, including when to round up for quieter filtration.
More guides
Dehumidifiers & humidity
30-Pint vs. 50-Pint DehumidifierBasement Dehumidifier Drainage ChecklistBest Dehumidifiers for BasementsBest Dehumidifiers for BedroomsDehumidifier Pint Size by Room TypeWhat Size Dehumidifier for a 1,000 Sq Ft Basement?What Size Dehumidifier for 1,500 Sq Ft?What Size Dehumidifier for 300 Sq Ft?What Size Dehumidifier for 800 Sq Ft?Humidifier vs. Dehumidifier
Electricity Cost GuidesCompare appliance watts, usage hours, rates, monthly totals, state averages, and common cost mistakes. 20 guides
Most useful
Costs
Summer Electric Bill Guide: AC, Fans, Dehumidifiers, and Pool Pumps
Estimate summer electric bill impact from window AC runtime, fans overnight, dehumidifiers, pool pumps, and your all-in kWh rate.
Costs
How to Estimate Electricity Cost for an Appliance
Use watts, hours, and your kWh rate to estimate daily, monthly, and yearly appliance electricity costs.
Costs
How Much Does It Cost to Run a Dehumidifier?
Estimate dehumidifier electricity cost from watts, runtime, duty cycle, humidity, and electricity rate.
Costs
How Much Does a Window AC Cost per Month?
Estimate monthly window AC cost from watts, runtime, duty cycle, electricity rate, room size, and seasonal use.
Costs
How Much Does a Fan Cost to Run Overnight?
Estimate overnight fan electricity cost from watts, hours, speed setting, and your kWh rate.
Costs
Pool Pump Electricity Cost by Hours per Day
Estimate pool pump electricity cost by pump watts, hours per day, days per month, and your electricity rate.
Costs
Average Electricity Cost by State
Learn how average electricity cost varies by state and why your all-in kWh rate may differ from published averages.
Costs
Electricity Cost Calculator by State
Use state electricity averages as a starting point, then estimate monthly cost with your actual watts and hours.
More guides
Heating, cooling, and summer costs
Aquarium GuidesUse these guides to check tank volume, heater watts, filter flow, substrate, water changes, and livestock-safe assumptions. 19 guides
Most useful
Aquarium
What Size Heater Do I Need for My Aquarium?
Choose aquarium heater wattage from tank gallons, room temperature, target water temperature, and safety margin.
Aquarium
What Size Aquarium Heater for a 75 Gallon Tank?
Estimate heater wattage for a 75 gallon aquarium and decide whether one heater or two smaller heaters makes more sense.
Aquarium
Aquarium Filter GPH for a 20 Gallon Tank
Estimate filter GPH for a 20 gallon aquarium and understand how media, flow loss, stocking, and plants change the target.
Aquarium
Aquarium Water Change Schedule Guide
Plan aquarium water changes by tank size, stocking level, change percentage, replacement-water temperature, and dechlorinator needs.
Aquarium
How Many Gallons Is My Fish Tank?
Calculate aquarium gallons from tank length, width, height, and displacement from substrate or decor.
Aquarium
Aquarium Heater Size for 10 Gallon Tank.
Estimate heater wattage for a 10 gallon aquarium based on temperature rise, room temperature, and practical heater placement.
Aquarium
What Size Heater for a 20 Gallon Aquarium?
Estimate aquarium heater wattage for a 20 gallon tank based on room temperature and target water temperature.
Aquarium
Aquarium Heater Size for 20 Gallon Tank.
Estimate heater wattage for a 20 gallon aquarium based on temperature rise, room temperature, and practical heater placement.
More guides
Heater sizing
Filters and flow
Home Improvement GuidesReview paint, primer, drywall, flooring, mulch, surface prep, waste, and measurement examples before buying materials. 13 guides
Most useful
Home Improvement
How to Calculate Paintable Wall Area
Estimate paintable wall area by measuring walls, subtracting large openings, planning coats, and adding a waste allowance before buying paint.
Home Improvement
How Many Gallons of Paint for a 12x12 Room?
Estimate paint gallons for a 12x12 room by wall height, coats, openings, paint coverage, and waste allowance.
Home Improvement
Paint for a 12x12 Room: Gallons, Coats, and Buffer
Plan paint for a 12 by 12 room using wall height, openings, coats, coverage, primer needs, and touch-up buffer.
Home Improvement
Flooring Waste Factor Guide
Learn how much extra flooring to order for simple rooms, closets, diagonal layouts, and patterned material.
Home Improvement
How Many Sheets of Drywall Do I Need?
Estimate drywall sheet count from wall and ceiling area, sheet size, waste, and project layout.
Home Improvement
Mulch Depth and Bag Guide
Choose a mulch depth and convert landscape area into bags, cubic feet, or cubic yards, with notes on bulk mulch, top-ups, and avoiding excess depth.
Home Improvement
Best Painting Supplies for Beginners
Build a beginner painting supply list with rollers, brushes, trays, tape, drop cloths, spackle, and prep tools.
Home Improvement
Caulk Bead Size and Tube Coverage Chart
Compare caulk bead sizes, estimated coverage per 10.1 fl oz tube, joint width, waste, and when to use the caulk calculator.
More guides
3D Printing GuidesPrice filament and resin jobs with slicer material, electricity, machine time, labor, failure risk, post-processing, and a clearly labeled profit method. 1 guides
Finance GuidesCompare retirement targets, FIRE timing, 401(k) growth, savings gaps, pay, work costs, payment, payoff, affordability, and household-budget assumptions. 11 guides
Most useful
Finance
Investment vs. High-Yield Savings: How to Compare the Tradeoffs
Compare investing with a high-yield savings account by timeline, volatility, liquidity, APY, fees, inflation, and the purpose of the money.
Finance
Credit card payoff date and extra payment guide
See how a fixed monthly payment changes payoff time and interest, how the final payment works, and why an issuer's payoff quote may differ.
Finance
Home Maintenance Reserve and Repair Planning Guide
Build an entered maintenance budget and repair-reserve catch-up plan without treating a percentage rule as a repair quote or insurance decision.
Finance
First Apartment Move-In Cost Checklist
Build an itemized first-apartment cash checklist for rent due, deposits, fees, utilities, moving supplies, prorated rent, and a separate cash buffer.
Finance
Gas vs. EV Driving Cost Guide
Compare gasoline and EV driving energy cost per mile and per year using the same annual miles, actual fuel price, and an all-in electricity rate.
Finance
Lease vs. Buy and Trade-In Equity Guide
Compare a written vehicle lease with buying over the same time horizon, then keep trade-in equity and any payoff gap visible before financing.
Finance
Move-Out, Rent Split, and Lease Cost Planning Guide
Plan a move-out budget by separating monthly affordability, upfront cash, roommate rent shares, and lease concessions before comparing apartments.
Finance
Remote, Hybrid, and Office Work Costs: Compare the Cash Difference
Compare office, hybrid, and remote annual cash costs using commute days, meals, childcare, home-office expenses, and other arrangement-specific inputs.
More guides
Teacher Tool GuidesPlan classroom rewards, behavior systems, fluency checks, grades, attendance, and teacher routines with clearer assumptions. 1 guides
ChartsPrintable charts and example pages are useful when you need a quick visual reference before opening a calculator. 34 charts
Most useful
Finance chart
Hourly Wage to Salary Chart
Compare hourly wages from $10 to $100 with weekly, biweekly, average monthly, and annual gross pay using one checked salary calculation source.
Home Air chart
Dehumidifier Size Chart by Room Size & Dampness
Use this dehumidifier size chart to compare room square footage, dampness level, and estimated pint capacity before opening the calculator.
Aquarium chart
Aquarium Heater Wattage Chart by Tank Size
Use this aquarium heater wattage chart to compare tank gallons, temperature rise, and suggested heater watts before opening the calculator.
Home Air chart
Air Purifier Room Size Chart
Use this air purifier room size chart to compare room volume, CADR, air changes per hour, and related sizing calculators before choosing a purifier.
Home Air chart
Air Purifier CADR Chart
Use this air purifier CADR chart to compare calculated clean air delivery targets by room size at four or five air changes per hour.
Home Improvement chart
Paint Coverage Chart by Room Size
Use this paint coverage chart to estimate paintable wall area, two-coat coverage, and gallons to buy for common room sizes.
Costs chart
Space Heater Electricity Cost Chart
Use this space heater electricity cost chart to compare heater wattage, daily runtime, kWh use, and monthly cost at an example electric rate.
Costs chart
Electricity Cost per Appliance Chart
Use this electricity cost per appliance chart to compare common wattages, run times, and monthly cost ranges.