While creating the % field you can specify the number of decimal places. This is standard functionality.

Then you can have a simple validation

ACC__C < 0 || ACC__C > 100

To limit values between 0 to 100. Or you can have just this validation. That should also work. On UI, the number would be rounded off.

As noted by sfdcfox below, please check the rounding off for record created via API.

While creating the % field you can specify the number of decimal places. This is standard functionality.

Then you can have a simple validation

ACC__C < 0 || ACC__C > 1

To limit values between 0 to 100. Or you can have just this validation. That should also work. On UI, the number would be rounded off.

As noted by sfdcfox below, please check the rounding off for record created via API.

While creating the % field you can specify the number of decimal places. This is standard functionality.

Then you can have a simple validation

ACC__C < 0 || ACC__C > 100

To limit values between 0 to 100. Or you can have just this validation. That should also work. The value will be rounded off.

While creating the % field you can specify the number of decimal places. This is standard functionality.

Then you can have a simple validation

ACC__C < 0 || ACC__C > 100

To limit values between 0 to 100. Or you can have just this validation. That should also work. On UI, the number would be rounded off.

As noted by sfdcfox below, please check the rounding off for record created via API.