A formula copied down a list normally moves its cell references with it. That is useful for the amount on each row, but wrong for a single conversion factor that every row should share.

Consider a simple test sheet: B2 contains 4 units, B3 contains 7 units, and F1 contains a fictional factor of 3. Enter =B2*$F$1 in C2. When filled down to C3, the row input becomes B3 while the shared factor remains F1. The expected results are 12 and 21.

Fix only the part that should remain fixed

In desktop Excel, dollar signs before both the column and row make $F$1 absolute for copying. A plain B2 is relative. A mixed reference fixes only one dimension, such as F$1 or $F1.

In Excel for Windows, selecting a reference while editing the formula and pressing F4 cycles through reference types. Read the resulting formula rather than counting key presses and assuming it reached the intended form.

Do not make every reference absolute. In the example, fixing B2 as well would make every result use the first row’s input. Decide which cells belong to each record and which are shared assumptions before filling a large range.

Inspect the first, second and final filled rows

Check the formula bar on C2 and C3 before extending the fill. Change the fictional factor temporarily and confirm that both outputs respond; then restore it. This tests the relationship rather than merely confirming that numbers appeared.

After filling the real range, inspect its last row and any row adjacent to a blank or subtotal. A correct initial formula does not prove that the fill covered exactly the intended records.

Keep the shared input clearly labelled with its meaning and units. Absolute references control how formulas are copied; they do not protect a cell from someone editing its value. That is a separate workbook design decision.

References: Microsoft: reference types.