Sum Calculator – Add Numbers & Arithmetic Series

Paste a list and every value is summed with a running total shown per line — handy for receipts, inventories and lab readings. For structured sequences the closed form skips the listing entirely: Gauss’s pairing computes 1+2+…+100 as 50 pairs of 101, so S₁₀₀ = 100×(1+100)/2 = 5,050. The calculator detects arithmetic patterns automatically: input 5, 9, 13, …, 201 (50 terms) and it applies Sₙ = n(a₁+aₙ)/2 = 50×(5+201)/2 = 5,150 rather than adding term by term. Geometric inputs like 3+6+12+…+1536 switch to Sₙ = a₁(rⁿ−1)/(r−1) = 3069. The parser accepts commas, spaces, tabs and newlines, ignores stray currency symbols, and reports count, sum, mean and largest/smallest alongside the total so one paste answers several questions at once.

1. 1

   Paste your numbers

   Separate by commas, spaces or newlines — mixed separators are fine

2. 2

   Scan the pattern

   The tool detects arithmetic or geometric sequences automatically

3. 3

   Apply the closed form

   Sₙ = n(a₁+aₙ)/2 or a₁(rⁿ−1)/(r−1) replaces term-by-term adding

4. 4

   Read the full statistics

   Count, sum, mean, min and max appear with the total

• 1

  Gauss pairing: first + last stays constant, so Sₙ = n(a₁+aₙ)/2

• 2

  Geometric sums need the ratio: 3+6+12+24 = 45 = 3(2⁴−1)/(2−1)

• 3

  Running totals catch transposition errors like 61 typed for 16

• Counting terms wrong: 5 through 201 stepping 4 is 50 terms, not 49

• Applying the arithmetic formula to geometric lists

• Missing negative signs on pasted debt values

• Mixing decimal separators (1,5 vs 1.5) across locales