Technique-verified 9x9 grids

18 hard Sudoku printables with answers

Every original puzzle has one solution, stalls below its named technique band, and completes without guessing when that strategy becomes available.

18 puzzles3 technique bands486 units checked27 PDF pages

Download the pack Preview real grids

Choose a hard Sudoku band

LOCKED CANDIDATES · 1–6

Connect boxes with lines

Singles stall. Pointing or claiming candidates unlock the grid.

PAIR LOGIC · 7–12

Restrict two possibilities

Locked candidates are not enough; a naked or hidden pair is required.

TRIPLE LOGIC · 13–18

Track three candidates

The pair-level solver stalls until a naked or hidden triple appears.

Print up to four hard sudoku grids per page

These files reformat the same 18 original puzzles, not 18 additional puzzles. Each file has 5 pages: the first four sheets have 4 grids each, and the final sheet has only puzzles 17 and 18.

Choose this compact layout to use fewer sheets. Keep the original full-page pack for larger writing spaces. Puzzle numbers and the original difficulty groups are unchanged; answers are in their own matching file.

US Letter puzzles - 5 pages US Letter answers - 5 pages A4 puzzles - 5 pages A4 answers - 5 pages

Print at actual size. Select a puzzle number and use the same number in the separate answer file.

Preview and choose a puzzle or answer page

Choose a page from the actual PDF contents. The links open the complete 27-page file at your selection when supported by your PDF viewer; they are not separate single-page files.

Puzzle, instructions or answer page

Open US Letter at page 1 Open A4 at page 1

In the print dialog, enter page 1 to print only that page. Some pages contain more than one puzzle or answer.

Actual printable US Letter page 1: Hard Sudoku 1: Locked Candidates — Actual US Letter PDF page 1. Select a page above to see its real contents. A4 uses its own print layout.

Ready-to-print pack

Download all 18 hard Sudoku

One roomy puzzle per activity page, with two solutions per answer page. No signup and no watermark.

Choose your paper sizeDownload US Letter PDF Download A4 PDFPrint at 100% or Actual Size.

Preview one real grid from each band

Locked Candidates#1

173574683727872645494575896235

30 givens · requires locked candidates

Pair Logic#7

81382216792861769276187252352

29 givens · requires naked or hidden pairs

Triple Logic#13

84359615796381954129636894

26 givens · requires naked or hidden triples

All 18 technique-verified puzzles

Puzzle	Band	Givens	Required	Trace steps	Answer
1	Locked Candidates	30	Locked candidates	59	19
2	Locked Candidates	28	Locked candidates	54	19
3	Locked Candidates	29	Locked candidates	56	20
4	Locked Candidates	31	Locked candidates	51	20
5	Locked Candidates	28	Locked candidates	54	21
6	Locked Candidates	30	Locked candidates	52	21
7	Pair Logic	29	Naked or hidden pairs	57	22
8	Pair Logic	28	Naked or hidden pairs	57	22
9	Pair Logic	28	Naked or hidden pairs	59	23
10	Pair Logic	28	Naked or hidden pairs	56	23
11	Pair Logic	26	Naked or hidden pairs	61	24
12	Pair Logic	27	Naked or hidden pairs	58	24
13	Triple Logic	26	Naked or hidden triples	61	25
14	Triple Logic	24	Naked or hidden triples	70	25
15	Triple Logic	25	Naked or hidden triples	66	26
16	Triple Logic	26	Naked or hidden triples	66	26
17	Triple Logic	27	Naked or hidden triples	62	27
18	Triple Logic	26	Naked or hidden triples	60	27

A candidate-marking workflow

1Exhaust naked and hidden singles.

2Write candidates in unresolved cells.

3Check pointing and claiming locks.

4Search for naked and hidden pairs.

5On the final band, inspect triples.

6Return to singles after every elimination.

How difficulty was checked

18 unique solutions

Every puzzle returns exactly one completion.

486 valid units

All rows, columns, and boxes were checked.

Lower cap stalls

Each band-defining technique is necessary.

Zero prior reuse

Boards, masks, and solutions are new.

Frequently asked questions

Are solutions included?

Yes. Pages 19-27 contain all 18 completed grids, with two solutions per page.

Are these hard only because they have fewer clues?

No. Given count is displayed, but the required strategy capability determines the band.

Do I need to guess?

No. Every puzzle completes within the disclosed singles, locked-candidate, pair, and triple ladder.

What should I try first?

Use the Easy Sudoku pack if you are still practicing naked and hidden singles.

Are Hard and Expert the same?

Publishers use different labels. This collection states its own reproducible technique boundary on every page.

Are Letter and A4 separate layouts?

Yes. Both editions contain identical puzzles on their true named paper dimensions.

See a real locked-candidate step in puzzle 1

This example follows the saved solving trace, not a made-up grid. Complete the prerequisite singles before comparing candidates. Coordinates use rows and columns numbered 1–9.

Preparation: the twelve preceding singles

r8c2 = 3; r8c3 = 1; r8c1 = 7; r8c6 = 4; r1c5 = 3; r6c9 = 7; r6c2 = 8; r9c5 = 7; r5c4 = 3; r5c6 = 8; r2c4 = 8; r7c9 = 3. Verify these against their rows, columns, and boxes; they are placements, not additional givens.

Hint 1: inspect box 2

Box 2 is the top-middle 3×3 box. After those singles, its remaining places for digit 1 are r3c4 and r3c5 and r3c6. Both lie in row 3, so the 1 for this box must be somewhere in row 3.

Hint 2: eliminate, do not place

Remove candidate 1 from row 3, column 8, which is outside box 2. This is a pointing-row elimination: it does not yet tell you which of the two box cells contains 1. Recheck the resulting singles before trying a more advanced technique.