How to Play on a 1 inch = 10 feet square grid.
I am the DM for a table top “Storm King’s Thunder” campaign. The final battle map is drawn in the book with one square = 10 feet. I usually draw the map on my battlemat with each 1 inch square = 5 feet. But this is such a large playing field that it won’t fit on my table at that scale so I am drawing it with 1 inch = 10 feet. I have occasionally done this before, but adjusting movements and attacks have always been a hassle. In anticipation of a large complicated battle I came up with this set of house rules.
To play with miniatures on a square grid where each square on the grid represents 10 feet:
Scale
Start with the rules in Variant: Playing on a Grid (PHB, page 192). Change “Each square on the grid represents 5 feet” to “Each (one inch) square on the grid represents 10 feet.”
Creature Size
For game purposes, creature sizes and speeds don’t change and if they have a 5 ft. reach they can attack creatures in adjacent squares even though creatures in adjacent squares are considered to be 10 ft. apart for all other purposes.
– Gargantuan Creatures
These each occupy a 2 inch square (four 1 inch squares).
– Large or Huge Creatures
These each occupy a single 1 inch square.
– Medium and Small Creatures
You can have more than one medium or small creature in one square. (I recommend flat, one inch diameter, tokens rather than minis. If there is more than one creature in a square you can stack them.)
A medium or small creature occupies one 1 inch square. Up to 4 creatures of this size can occupy a single square, but they are each considered occupying the entire square. If there is more than one such creature in a square they are considered to be 5 feet apart from each other.
A single medium or small creature can not be attacked by more than 8 medium or small creatures (or 4 large or larger creatures) with 5 ft. melee attacks.
– Tiny Creatures
You can stack 16 tiny creatures in one square. They are considered to be 2 1/2 ft. apart. You can have a combination of tiny and medium or small creatures. There can be a maximum of: 1 medium or small and 12 tiny, 2 medium or small and 8 tiny, or 3 medium or small and 4 tiny.
Movement
Speed and movement doesn’t change, but you can’t move into a square if you don’t have enough movement left (10 feet).
Example: If your move rate is 25 feet, you can only move 2 squares (25 ft. rounded down = 20 ft.), but if you dash you can move 5 squares (25 ft. x 2 = 50 ft.).
Medium or small creatures can move through, but not stop in, a square occupied by a Gargantuan or Huge creature but it can’t move through a square occupied by a Large creature.
Medium or small creatures can move through, or stop in if they choose to, a square occupied by fewer than 4 medium or small creatures, regardless if the occupying creatures are hostile or not. If it is occupied by 4 non-hostile creatures you can move through it but you can not stop in it.
Ranges and areas of effect:
All ranges and areas of effect are rounded down to a multiple of 10 feet (minimum of 10 feet).
Some examples: All melee attacks with a range of 5 feet will have a range of 10 ft. (or, rather, they are treated as if they were actually only 5 ft. away.) So you can attack a creature in an adjacent square with your short sword, or you could attack it with your long bow without disadvantage because, for everything other than 5 ft. melee attacks, it is 10 ft. away. For the same reason an attack on a prone creature in an adjacent square is with advantage if you make a 5 ft. melee attack (it’s 5 ft. away), but it is with a disadvantage if it is made with range weapon (it’s 10 ft. away). A blowgun’s range changes from (25/100) to (20/100). The spell Word of Recall‘s range changes from 5 ft. to 10 ft. The spell Lightning Bolt will form a line 10 ft. wide instead of 5 ft. The Gust of Wind spell will push a creature 10 ft. instead of 15 ft.
Opportunity Attacks
Your 5 ft. reach becomes 10 ft. in regard to creatures in adjacent squares. So if a hostile creature moves out of an adjacent 10 ft. square you can make an opportunity attack against it. But if it moves from within the same square you are in to an adjacent square you can not (because it will still be within range).
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Dungeon Master Assistance 
Interesting! I’ve done this when I DM for my groups, and I really like the results.
How my group differs is that creatures can occupy the same square up to a certain number: up to four Medium creatures can occupy the same square. If a sqaure is over-filled, the creature that last entered is forced out and triggers an attack of opportunity.
Second difference is that I rule that you can still move one sqaure if you have at least 5 more feet of movement. So 25ft can still move three squares.
Some interesting apects I found when doing things this way:
1. Range and movement becomes extra important, which makes even simple empty rooms have some dynamics and interesting choices.
2. It becomes easy to determine at a glance which creatures are engaged in combat with whom. Attack fo opportunity are also triggered when a creature moves out of the square.
3. Flanking can be determined without facing: If a creature is an a square with enemies, and is outnumbered, the creature is considered flanked. e.g. Two heroes fighting against an orc in a sqaure, the orc is considered flanked. You can even make flanking granular (+2 if outnumbering target by one, +5 if outnumbering target by two).
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Ezekiel, thank you for your comment.
It looks like you are giving everyone a little extra movement and I am reducing their movement a little. I considered doing it your way but decided against it. I couldn’t think of a good argument ether way, so I just went to the default for 5th edition and and round all fractions down. It would be interesting to try it both ways and see which worked better, and why.
I don’t currently use flanking and hadn’t considered how 10 ft. squares might make flanking easier. I love your idea regarding this and will consider using it in my game.
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Reblogged this on DDOCentral.
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I have a video on running combat without a grid, check it out if your intrested https://youtu.be/tCLaxQdXDaA
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I highly recommend everyone check out this video!
This is a great idea. I have always played on a grid and your idea just never occurred to me. The next time I run a game at a game store I will seriously consider doing it your way. Carting a battlemat around is a pain. The only problem that I see is that if you don’t have all of the 3D terrain and walls you need you will still need to draw floor plans for dungeons, etc.
You may be interested in something I use occasionally, and will be using a lot if I go gridless. It is a home-made tape measure marked off in feet at a 1 inch = 5 feet scale. Here is what I did:
I took a toy tape measure (see link below). It is a vinyl tape marked with only inches. First I removed the tape from its large plastic housing. That part is made for small kids and I found it more of a hindrance than a help. Using a Sharpie I marked each inch with the number of feet. Without all of the typical marks for fractions of an inch it leaves plenty of room on this wide white vinyl tape to to make the feet markings easy to read.
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Thank you, I am trying this.
I wanted to go to 10 foot spaces because I want to add tactical elements to the combat. In fact, I’m using the Gloomhaven board and pieces to represent. I am just sick of everything being in range and everyone being able to get everywhere all of the time… feels like a missed opportunity. (example: spells have 60 or 120 ft. range but it’s meaningless because 120 feet is a BIG map area if they’re only 5′ squares).
Anyway, thanks for the practical advice. One thing I’m going to do differently is allow one of my player’s grapple character to continue to move 2 squares if grappling (speed is 25) because I don’t want to reduce him to 1 most of the time.
Thank you again!
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Or you could remove the restriction that I suggested, that “you can’t move into a square if you don’t have enough movement left”. Some others have done this and I may also the next time I play on 10′ squares.
What this does is allow all of the PCs, whether they have a 25 or 30 ft speed, move 3 squares normally and 2 squares at half speed. But if they dash, the slower characters still moves 5 squares (25ft. X 2 = 50 ft) and the faster characters still move 6 squares (30ft. X 2 = 60 ft).
I am glad this helps.
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