REFERENCE MANUALREFERENCE

REFERENCE MANUALREFERENCECALCULATE · DECIDE · ACT

Formula reference

Useful calculator formulas, in plain English.

A consolidated reference for the equations and worked examples behind tannerd.net's highest-value calculators. Use the linked calculator when you want the interactive version.

Reviewed September 1, 2026

Seller & ecommerce

Seller profit quick answer

Seller Profit Calculator – Fees, Shipping & ROI

Seller profit is the sale price minus the item cost, marketplace or payment fees, shipping, and other direct selling costs.

Formula: Profit = sale price − item cost − selling fees − shipping − other direct costs. ROI = profit ÷ item cost × 100. Profit margin = profit ÷ sale price × 100.

Example: If an item costs $50, sells for $200, has $26 in fees and $20 in shipping, estimated profit is $104 before taxes and overhead.

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Ecommerce profit quick answer

Ecommerce Profit Calculator

Ecommerce profit per order is what remains after product cost, shipping, fulfillment, transaction fees, advertising, and other variable order costs are subtracted from order revenue.

Formula: Profit per order = order revenue − COGS − shipping − fulfillment − fees − advertising − other variable costs.

Example: An $80 order with $25 product cost, $6 shipping, $3 fulfillment, $2.40 in fees, and $18 ad cost leaves $25.60 in modeled order profit.

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Break-even ROAS quick answer

Break-even ROAS Calculator

Break-even ROAS is the minimum return on ad spend at which the contribution available before advertising is fully consumed by ad cost.

Formula: Break-even ROAS = order revenue ÷ maximum allowable ad spend. Equivalently, break-even ROAS = 1 ÷ contribution margin rate before ads.

Example: If an $80 order has $42.60 available before ads, break-even ROAS is about 1.88×.

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ROAS quick answer

ROAS Calculator

Return on ad spend measures attributed revenue generated for each dollar of advertising spend.

Formula: ROAS = attributed revenue ÷ ad spend.

Example: $5,000 of attributed revenue from $1,500 of ad spend equals a 3.33× ROAS.

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Contribution margin quick answer

Contribution Margin Calculator

Contribution margin is the revenue left after variable costs and is the amount available to cover advertising, fixed overhead, and profit.

Formula: Contribution dollars = revenue − variable costs. Contribution margin % = contribution dollars ÷ revenue × 100.

Example: $80 revenue with $36.40 of variable cost leaves $43.60 contribution, or a 54.5% contribution margin.

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Customer acquisition cost quick answer

Customer Acquisition Cost Calculator

Customer acquisition cost (CAC) is the average acquisition spend required to generate one new customer.

Formula: CAC = sales and marketing acquisition spend ÷ new customers acquired.

Example: $5,000 of acquisition spend that produces 125 new customers equals a $40 CAC.

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Target sale price quick answer

Target Profit Sale Price Calculator

A target-profit sale price works backward from item cost, desired profit, fixed selling costs, and percentage fees to find the price required to reach the target.

Formula: Required sale price = (item cost + target profit + fixed selling costs) ÷ (1 − percentage fee rate).

Example: A $50 item, $100 target profit, $20 fixed selling costs, and a 13% fee requires a sale price of about $195.40.

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Seller net proceeds quick answer

Seller Net Proceeds Calculator

Seller net proceeds are the sale price remaining after marketplace fees, seller-paid shipping, and other selling expenses, before subtracting the original item cost.

Formula: Net proceeds = sale price − selling fees − seller-paid shipping − other selling costs.

Example: A $200 sale with $26 in fees and $20 seller-paid shipping leaves $154 in net proceeds before item cost.

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Work & pay

Time card quick answer

Time Card Calculator

A time card total is the sum of each paid shift: clock-out time minus clock-in time minus unpaid breaks. Overnight shifts carry the end time into the next day.

Formula: Paid daily hours = elapsed shift time − unpaid break. Weekly regular and overtime hours are then split at the overtime threshold entered in the calculator.

Example: Five 8-hour paid days plus a 6-hour Saturday equal 46 hours. With a 40-hour threshold, that is 40 regular hours and 6 overtime hours.

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Shift pay quick answer

Shift Pay Calculator

Shift pay is paid shift hours multiplied by the hourly rate after subtracting any unpaid break.

Formula: Gross shift pay = (elapsed shift hours − unpaid break hours) × hourly rate.

Example: A 1:30 PM–1:30 AM shift with a 30-minute unpaid break is 11.5 paid hours. At $20/hour, gross straight-time pay is $230.

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Shift hours quick answer

Shift Hours Calculator

Shift hours are the elapsed time from clock-in to clock-out minus any unpaid break. An end time earlier than the start time is treated as the following day.

Formula: Paid hours = elapsed minutes ÷ 60 − unpaid break minutes ÷ 60.

Example: 7:30 PM to 1:30 AM is 6 hours. With a 30-minute unpaid break, paid time is 5.5 hours.

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Overtime quick answer

Overtime Calculator

This calculator separates hours above the entered weekly overtime threshold and applies an overtime multiplier to those hours.

Formula: Gross pay = regular hours × regular rate + overtime hours × regular rate × overtime multiplier.

Example: At $20/hour, 45 hours with a 40-hour threshold and a 1.5× multiplier produces $950 in modeled gross pay.

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Driving

Trip gas cost quick answer

Gas Trip Cost Calculator – Mileage, MPG & Fuel Price

Trip gas cost is based on the number of gallons needed for the distance and the price paid per gallon.

Formula: Gallons needed = trip miles ÷ MPG. Gas cost = gallons needed × gas price per gallon.

Example: A 300-mile trip at 30 MPG uses about 10 gallons. At $3.25 per gallon, estimated gas cost is $32.50.

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Cost per mile quick answer

Cost Per Mile Calculator – Dollars & Price Per Mile

Cost per mile spreads the vehicle or operating costs you choose across the miles driven over the same period.

Formula: Cost per mile = total costs ÷ total miles. Revenue per mile = total revenue ÷ miles. Profit per mile = (revenue − costs) ÷ miles.

Example: $800 of costs over 2,000 miles equals $0.40 per mile. If those miles generated $1,600, revenue is $0.80 per mile.

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Gas cost per mile quick answer

Gas Cost Per Mile Calculator

Gas cost per mile converts MPG and fuel price into the fuel expense of driving one mile.

Formula: Gas cost per mile = price per gallon ÷ vehicle MPG.

Example: At 30 MPG and $3.25 per gallon, fuel costs about $0.108 per mile.

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Gig driving profit quick answer

Gig Driver Profit Calculator

Gig driving profit is gross gig earnings minus the vehicle cost assigned to the miles driven.

Formula: Estimated profit = gross earnings − (total miles × estimated vehicle cost per mile). Effective hourly profit = estimated profit ÷ hours worked.

Example: $250 gross earnings over 200 miles with a $0.35-per-mile vehicle cost leaves about $180 before taxes and other non-vehicle expenses.

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Home improvement

Roof material takeoff quick answer

Roof Material Takeoff Calculator

A roof material takeoff converts the roof footprint and pitch into adjusted roof area, then applies waste and product coverage to estimate shingles and related materials.

Formula: Adjusted roof area = footprint area × pitch multiplier × (1 + waste rate). Roofing squares = adjusted roof area ÷ 100.

Example: The calculator turns the adjusted area into roofing squares, bundles, underlayment, ridge-cap, drip-edge, and nail estimates using the coverage assumptions shown on the page.

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Roofing squares quick answer

Roofing Squares Calculator

One roofing square represents 100 square feet of roof area. Waste is normally added before converting the final area to squares.

Formula: Roofing squares = adjusted roof area ÷ 100.

Example: 2,200 square feet of adjusted roof area equals 22 roofing squares.

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Shingle bundles quick answer

Shingle Bundles Calculator

Shingle bundle quantity depends on roof squares and the number of bundles required per square for the specific shingle product.

Formula: Bundles needed = roofing squares × bundles per square, rounded up as needed.

Example: At three bundles per square, 22 roofing squares require about 66 bundles before any additional product-specific allowance.

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Concrete slab quick answer

Concrete Slab Calculator

Concrete slab volume is the slab length multiplied by width and thickness, converted into cubic yards for ready-mix ordering.

Formula: Cubic yards = length (ft) × width (ft) × thickness (ft) ÷ 27. Apply the chosen waste allowance after calculating base volume.

Example: A 10 ft × 10 ft slab that is 4 inches thick is about 1.23 cubic yards before waste.

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Concrete bag quick answer

Concrete Bag Calculator

Concrete bag count is the required concrete volume divided by the yield of the bag size selected, rounded up to whole bags.

Formula: Bags needed = required cubic feet ÷ cubic feet yielded per bag.

Example: The calculator uses the selected bag-yield assumption shown on the page and rounds up because partial bags cannot normally be purchased.

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Drywall material quick answer

Drywall Material Calculator

Drywall material quantity starts with wall and ceiling surface area, then divides by panel coverage and adds the selected waste allowance.

Formula: Panels needed = total drywall area × (1 + waste rate) ÷ square feet covered per panel, rounded up.

Example: A 4×8 drywall sheet covers 32 square feet before cuts and waste.

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Room paint quick answer

Room Paint Calculator

Paint quantity is based on paintable wall area, the number of coats, and the coverage rate of the paint being used.

Formula: Gallons needed = paintable square feet × coats ÷ coverage square feet per gallon, rounded up for purchasing.

Example: Coverage varies by product and surface, so the calculator keeps the coverage assumption visible and editable.

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Flooring material quick answer

Flooring Material Calculator

Flooring material quantity is room area plus a waste allowance for cuts, pattern matching, defects, and future repairs.

Formula: Adjusted flooring area = room area × (1 + waste rate).

Example: A 200-square-foot room with 10% waste calls for about 220 square feet of flooring material.

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Fence material quick answer

Fence Material Calculator

Fence material planning starts with total fence length and spacing, then rounds posts, sections, pickets, rails, and concrete to practical whole quantities.

Formula: Fence sections are based on total run length ÷ section or post spacing, with endpoints and gates handled as entered.

Example: Because real layouts depend on corners and gates, the calculator exposes the spacing assumptions rather than hiding them.

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Contractor markup and margin quick answer

Contractor Markup & Margin Calculator

Markup measures profit relative to cost, while margin measures profit relative to the final selling price. The percentages are not interchangeable.

Formula: Markup % = profit ÷ cost × 100. Margin % = profit ÷ selling price × 100.

Example: A $100 cost sold for $150 has a 50% markup but a 33.3% gross margin.

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How these references are maintained

Arithmetic formulas are shown directly. When a calculator depends on variable product coverage, waste allowances, overtime thresholds, marketplace fees, or other assumptions, the calculator exposes those assumptions rather than presenting one changing value as universal. See the methodology page for review standards.