Change a measurement. Keep your work.

A feet and inches calculator for work you need to revise

TapeSum is a construction measurement calculator for iPhone, with iPad layouts too. It handles feet, inches and fractions in editable rows, so a corrected dimension changes the result without clearing the other inputs. Use it for measurement arithmetic, rectangular area and a record you can return to—not material estimates or structural calculations.

Add feet and inches with fractions

Example: 12′ 3 1/2″ + 8′ 7 3/4″ = 20′ 11 1/4″.

To check this by hand, add like units and carry any full inches or feet:

1. Add the fractions: 1/2 + 3/4 = 2/4 + 3/4 = 1 1/4 inches.
2. Add the inches, including the carried inch: 3 + 7 + 1 1/4 = 11 1/4 inches.
3. Add the feet: 12 + 8 = 20 feet. The final result is 20′ 11 1/4″.

If your inches total reaches 12, carry 12 inches into one foot. In TapeSum, enter the first measurement, add a row, then enter the second measurement. You can read the exact total and the selected tape-rounded total separately.

Now suppose the first dimension changes to 12′ 4 1/2″. Edit that row only: the total becomes 21′ 0 1/4″. The second measurement stays in place. That is the benefit of an editable measurement worksheet when a trim run or installation dimension changes.

Subtract a mixed measurement

Example: 10′ 0″ − 3′ 7 5/8″ = 6′ 4 3/8″.

One way to verify subtraction is to work in inches. Ten feet is 120 inches, and 3′ 7 5/8″ is 43 5/8 inches. Subtract to get 76 3/8 inches, then divide the whole inches into feet: 72 inches is six feet, leaving 4 3/8 inches.

In the app, choose the minus operator between those two measurements. Multiplication and division use a scalar—a number such as 2—rather than another length. Those operations are evaluated before addition and subtraction. Use the dedicated Rectangle Area mode for length × width.

Round to the nearest 1/16 inch

Example: 7 3/32″ becomes 7 1/8″, a difference of +1/32 inch.

The adjacent sixteenth-inch marks are 7 1/16″ and 7 1/8″. The exact value sits halfway between them. TapeSum’s nearest mode rounds midpoints away from zero, so this positive example goes to the higher mark.

Rounding mode	Tape result	Tape result minus exact result
Nearest	7 1/8 in	+1/32 in
Down	7 1/16 in	−1/32 in
Up	7 1/8 in	+1/32 in

Choose increments from 1/2 through 1/64 inch. Down means toward negative infinity and Up means toward positive infinity, including for negative results. Rounding changes the displayed tape value; it does not make the original measurement more precise. Check the signed difference before deciding which mark fits your work.

For an increment of 1/n inch, TapeSum rounds exact inches × n to a whole tape tick, then divides by n. Nearest uses midpoint ties away from zero; Down uses floor and Up uses ceiling. The signed rounding difference is rounded inches − exact inches. For example, −7 3/32″ rounds to −7 1/8″ in nearest mode, while Up gives −7 1/16″. These are calculation rules, not advice about acceptable construction tolerances.

Calculate rectangle square footage

For a rectangle measuring 12′ 3 1/2″ by 8′ 7 3/4″, the area is approximately 106.2717 sq ft.

Convert the lengths to inches: 147 1/2 × 103 3/4 = 15,303 1/8 square inches. There are 144 square inches in one square foot, so divide by 144. The exact square-foot result is 106 313/1152 sq ft; 106.2717 is a truncated decimal display, not a replacement for the exact fraction.

In Rectangle Area, enter positive length and width and a positive whole-number quantity. For repeated identical rectangles, quantity multiplies the area. Tape rounding does not change the dimensions used in this workflow. The result is geometric area; it does not include waste, material coverage, openings or prices.

The unit relationships—12 inches per foot and 144 square inches per square foot—are documented in NIST’s tables of units.

The reusable area formula is square feet = length in inches × width in inches × quantity ÷ 144. TapeSum requires positive dimensions and a positive whole-number quantity. These worked examples describe TapeSum’s current pre-release calculation behavior; they do not imply an available App Store release.

Keep a worksheet you can return to

For example, name a worksheet “Porch trim” and save a calculation for each measured run. If one run changes, reopen that calculation and edit its input. Make a copy first when you want to compare an alternative without replacing the saved version.

History is the automatic record of completed calculations. A worksheet is the named collection you deliberately save. A shared summary includes the original measurements, results and rounding details so someone else can check the calculation. Sharing produces plain text, not a PDF or a restorable backup.

Before you choose TapeSum

Can I enter fractions without converting to decimals?

Yes. Use forms such as 12' 3 1/2", 8', 7 3/4" or 3/8". Unmarked numbers are inches. Decimal input is also accepted with your local decimal separator. Measurement-entry help explains the notation.

Does it work without an account or internet connection?

Measurement calculations and local worksheets do. Purchase options, restores and entitlement refreshes use Apple and RevenueCat. Sending a shared summary through another app may require a connection. See the privacy policy for the distinction between local content and purchase data.

What is included free?

Measurement math, rectangle area, tape rounding, history and sharing, plus one worksheet with up to three saved calculations. Pro removes those saved-capacity limits. Existing saved work remains accessible without active Pro access. The optional guide and paywall can be dismissed.

Does it calculate roofing, stairs or material estimates?

No. TapeSum focuses on length arithmetic, rectangle area and revisable worksheets. It does not provide roofing, stair, structural, building-code or estimating tools.

These examples were checked using exact rational arithmetic. For an input or saved-work problem, visit TapeSum support or contact tapesum@gmail.com.