(Excel)Calculating costs, where prices differ based on quantities - excel

Question

I'm looking for some help as I'm not really sure of the correct terms to use on my query below, so whilst normally I would google this, I'm not really sure what to search for.
I need to work out the total cost for something, where you have a flat rate, and then an additional cost that changes depending on how much of something you have.
So an example, you get expenses paid for millage. If you drive 0-20 miles, you'll get £10. Between 30-50 miles you get 50p per mile. Between 51-100 miles you get £1 per mile and so on, added onto the base rate of the initial £10 you'd get paid as standard.
It's not the best example, but hoping it gives an idea of what I'm after.
If I was doing this by hand I'd know how to work it out, but I'm not to sure what kind of formula I need to be using - I've never had to work with complex formulas past "=sum" until now.
If anyone has any examples they can share or can point me in the right direction of what kind of things to google I'd be most grateful !
Thanks

Answer 1

Well, here is one way, but you don't state what the rate is between 21 and 30...
very basic, but you should be able to edit and expand as you want.
Do note that the limits (30 miles, 50 miles) and rates used in the formula all come from the sheet - so if the 30 mile limit changes to 25 miles - all you need to do is change cell A7...

Answer 2

I apologize for not answering sooner, but I find this question a bit difficult to address due to the complexity of formulas we can encounter. I know the one you documented is not the most complex one we might encounter, but I was not sure if that was your actual problem or if it was intended as a simple example. I have seen a variety of other things which have often thrown me for a loop.
For example, take this set of rules:
Minimum Fee is $23.50 up to $500
$501 - $2,000 = $3.05 per 100 unit increment
$2,001 - $25,000 = $14.00 per 1000 unit increment over $2,000
$25,001 - $50,000 = $10.10 per 1000 unit increment over $25,000
$50,001 - $100,000 = $7.00 per 1000 unit increment over $50,000
$100,001 - $500,000 = $5.60 per 1000 unit increment over $100,000
$500,001 - $1,000,000 = $4.75 per 1000 unit increment over $500,000
$1,000,001 - $9,999,000 = $3.65 per 1000 unit increment over $1,000,000
$10,000,001 and up = $3.65 per 1000 unit increment over $10,000,000
It does not look too different from yours except that there is an increment of something other than a single unit. In other words for the $501 to $2,000 range, $501 to $600 would all get the same additional $3.05 incremental charge. Another dollar would actually double this because it jumps to the next increment. Like your example, each range builds on the prior range. Assuming that these amounts are in colums A through F:
i Low High Fee Base Fee Per
0 1 500 23.50
1 501 2,000 $3.05 100
2 2,001 25,000 $23.50 1000
3 25,001 50,000 $10.10 1000
4 50,001 100,000 $7.00 1000
5 100,001 500,000 $5.60 1000
6 500,001 1,000,000 $4.75 1000
7 1,000,001 9,999,999 $3.65 1000
8 10,000,000 $3.65 1000
Note also that the rate declines as the amounts increase whereas yours appears to increase.
What I did with this is create a maximum value in Column H as follows:
i Max
0 =E3
1 =INT((C4-C3)/F4)*D4
2 =INT((C5-C4)/F5)*D5
3 =INT((C6-C5)/F6)*D6
4 =INT((C7-C6)/F7)*D7
5 =INT((C8-C7)/F8)*D8
6 =INT((C9-C8)/F9)*D9
7 =INT((C10-C9)/F10)*D10
8
The first one, where i is zero, is simply the base fee. The others are computed and copied. There is no maximum for the last row. I did not really think I needed this column but it made it easier to devise the formulas.
Assuming that I put an amount to evaluate in Cell I2, it will be evaluated as follows where the formula in row 3 (where i=0) is the set fee but all others are basically a copied formula:
i 4,950
0 =IF(I$2>=$B3,$H3,0)
1 =IF(I$2>=$B4,IF($H4="",INT((I$2-$C3)/$F4)*$D4,MIN($H4,INT((I$2-$C3)/$F4)*$D4)),0)
2 =IF(I$2>=$B5,IF($H5="",INT((I$2-$C4)/$F5)*$D5,MIN($H5,INT((I$2-$C4)/$F5)*$D5)),0)
3 =IF(I$2>=$B6,IF($H6="",INT((I$2-$C5)/$F6)*$D6,MIN($H6,INT((I$2-$C5)/$F6)*$D6)),0)
4 =IF(I$2>=$B7,IF($H7="",INT((I$2-$C6)/$F7)*$D7,MIN($H7,INT((I$2-$C6)/$F7)*$D7)),0)
5 =IF(I$2>=$B8,IF($H8="",INT((I$2-$C7)/$F8)*$D8,MIN($H8,INT((I$2-$C7)/$F8)*$D8)),0)
6 =IF(I$2>=$B9,IF($H9="",INT((I$2-$C8)/$F9)*$D9,MIN($H9,INT((I$2-$C8)/$F9)*$D9)),0)
7 =IF(I$2>=$B10,IF($H10="",INT((I$2-$C9)/$F10)*$D10,MIN($H10,INT((I$2-$C9)/$F10)*$D10)),0)
8 =IF(I$2>=$B11,IF($H11="",INT((I$2-$C10)/$F11)*$D11,MIN($H11,INT((I$2-$C10)/$F11)*$D11)),0)
The Fee for this is the sum of all of the rows (labeled i, 0 through 8 above). in this example, it would be 23.50 plus 45.75 plus 28.00 for a total of 97.25.
Not too bad. How about a set like this:
No fee if $1,000 or less
$1,001 - $5,000 = $80.00 + 3% of excess over $1,000.00 per 100 unit increment
$5,001 - $10,000 = $250.00 + 2% of excess over $5,000.00 per 500 unit increment
$10,001 - $25,000 = $350.00 + 1% of excess over $10,000.00 per 1000 unit increment
$25,001 and Over = $520.00 + 3/4% of excess over $25,000.00 per 1000 unit increment
In your formula, the initial flat amount never changes and once you've computed the amount for that range, other ranges build upon it. Here, there are steps. For example at $1,000 the fee is zero, but at $1,001, it jumps to $80 as if there were an $80 fee for the first 1000. Without boring you with the entire table, Here is the formula for computing the range from 5,001 to 10,000 assuming that G2 contains the amount to use and Row 5 colums A through E are the following:
Low High Rate Minimum Increment
5,001 10,000 2.00% 250 500
=($D5+$C5*INT(($G$2-($A5-1))/$E5)*$E5)*($G$2>=$A5)*OR($B5="",$G$2<=$B5)
The formula simply looks at the current row and does the computation if the amount in G2 falls within the range from Column A to Column B.
A simplification of all of the above comes when each range cumulatively builds on the prior ranges AND the rate of payment is always increasing, like the U.S. Tax Tables:
Over Not Over
0 9,525 10% of taxable income
9,525 38,700 $952.50 plus 12% of the excess over $9,525
38,700 82,500 $4,453.50 plus 22% of the excess over $38,700
82,500 157,500 $14,089.50 plus 24% of the excess over $82,500
157,500 200,000 $32,089.50 plus 32% of the excess over $157,500
200,000 500,000 $45,689.50 plus 35% of the excess over $200,000
500,000 $150,689.50 plus 37% of the excess over $500,000
Here, we can use something referred to as the "deskpad method" to shortcut the computation
Assuming that the amount to be evaluated is in G1 and these are in column A through C starting in Row 1:
Over Not Over Rate
0 9,525 10.0%
9,525 38,700 12.0%
38,700 82,500 22.0%
82,500 157,500 24.0%
157,500 200,000 32.0%
200,000 500,000 35.0%
500,000 37.0%
We compute the amount based on G1 as follows:
=ROUND(SUMPRODUCT($C$2:$C$8-$C$1:$C$7,$G$1-$A$2:$A$8,N($G$1>$A$2:$A$8)),0)
Note: this is not entered as an array formula.
How does this relate to your question. If the need is as simple as you stated (in other words, the rate is always increasing and we do not have any "steps" in the reimbursement, we can compute it similarly to the U.S. Tax computation.
I created these values in columns A through D starting in row 1:
Over Not Over
0 20 £- Flat Amount of £10.00
20 50 £0.50 £10.00 plus £.50 per mile over 20 miles
50 100 £1.00 £25.00 plus £1.00 per mile over 50 miles
100 £1.50 £75.00 plus £1.50 per mile over 100 miles
where column D is just descriptive. I put the £10.00 flat fee in Cell E1.
Assuming that G1 contains the number of miles, we would compute the reimbursement as:
=$E$1+ROUND(SUMPRODUCT($C$2:$C$5-$C$1:$C$4,$G$1-$A$2:$A$5,N($G$1>$A$2:$A$5)),2))
For example, when G1 is 52 miles, the computation is £27.00
Note: this is not entered as an array formula.
So, if this is the situation, what you would need is a place to house Columns A through C, a place to house the flat amount and a formula similar to what I provided to compute the reimbursement based on the cell housing the number of miles.
Please note that all the earlier items indicate that this formula will not be so simple if the rate is stepped or the rate declines or if the incremental unit is something other than 1 mile.
I hope that some of this makes sense. Good luck.

Answer 3

Things to google : "nested IF in excel"
How to do this in a one-line-formula : enter " =IF(A1<20,10,IF(A1>50,IF(A1>50,10+A1,"u"),0.5*(A1))) " in B1, your milage in A1.
To learn building this :
identify the conditions :
condition1 > 0-20 miles, you'll get £10.
condition2 > between 30-50 miles you get 50p per mile
condition3 > between 51-100 miles you get £1 per mile added onto £10
put the conditions into IF() statement
For contition1 > just type " =if(a1<20,10,0) " at B2 (and try it!) (:
Note : The syntax for IF() function is if("condition","if-true-do-this","if-false-do-this")
Thus, for condition2 > " =if(a1>20,a1*0.5,0) "
And for condition3 > " =if(a1>50,if(a1>50,10+a1),0) " correction : should be " =if(a1>50,10+a1,0) "
Combining all the conditions > "=IF(A1>20,IF(A1>50,IF(A1>50,10+A1,"error"),0.5*(A1)),10) "
Notice that I changed 0 in the "if-false-do-this" part of the equation just to make sure it show something when the milage entered is less than 0.
Hope that helps. /(^_^)